This summer I met a man in Germany who had lost more than 40 pounds while training for a half-marathon. He used a heart rate monitor to keep his pulse in the optimum fat burning zone and said, "It really works." I wanted a heart rate monitor that reads constantly and I can see while riding my bicycle, especially as winter approaches.

I chose the Sigma because the user can change the battery in the chest strap without sending it back to the factory. I like the digital packet transmissions that block interference from electrical lines and traffic lights.

The BC 2006 works well. I have lost pulse and MPH readouts a couple of times. Once this was due to lost electrical connection between the chest strap and my skin. Moistening my skin with water before putting the chest strap on helps. Once the chest strap changed its position on my skin and I lost the signal for a while. Tightening the strap a bit helps. Low batteries in the chest strap or the wheel sensor causes no readings, too. And, I often ride without my eyeglasses and it would be helpful if the pulse readout had a larger display.

The initial programming is involved and a little confusing. At times a bit more information in the manual would be helpful. A table of programming numbers for different wheel and tires sizes is given. But, it would be more helpful if the manual mentioned these are the circumference of the wheel with tire. I did not change wheels, but changed tires and the circumference changed, even though the size of the tires is the same. I measured the distance my tire rolls during one rotation with my weight on the bike and had to change the figure I entered in order to maintain accuracy.

The altimeter function is interesting. I am still learning to program and use it. It would have been more helpful to have a cadence function.

Yes, this bicycle computer allows its use on two bicycles and it automatically knows which bike is in use. What you do not know until the box arrives is that the second sender unit costs an additional $25 plus shipping. An extra magnet for $7 plus shipping would be advisable. Also needed is a second mounting bracket for the handlebars. That costs another $8 plus shipping. No information on ordering these things is given in the manual. You need to go to Sigma's web site and search their on-line store.

The Sigma comes with two backs. One automatically brings up a display for cycling. The other automatically brings up a display for running or walking. The second back allows the user to check his pulse while using any exercise equipment, like a NordicTrack ski machine. Because the unit twists off from the back, you can take your Sigma with you when you must lock your bike and leave it somewhere. Once the display unit came off of the bike while I was transporting the bike in the back of my wife's small SUV. Once readings disappeared because vibration had caused the display unit to twist just a bit loose.

Experience so far indicates this unit will help me lose weight, althought slowly. It is far less expensive than a health club membership.

UPDATE: No one knows how long one of these units may have been on a warehouse shelf. The sensors (chest strap and wheel) are draining power from their batteries the whole time. One day I got no heart or speed readings. I changed batteries in the sensors and everything is perfect. I do not lose signals at all, now.

All batteries (3) are # CR-2032 "watch batteries." A new one reads 3.3 volts. When they go down to 3.0 volts, they are no longer reliable. You might want to install new batteries when you get your new Sigma, just to have a more enjoyable experience with it. The wheel sensor battery lasted only three to four weeks. I contacted Sigma's North American office and they very kindly exchanged my wheel sensor for a replacement. The battery in it seems to last much, much longer now.
5 stars

This is my second German-made computer (the other was a Ciclo). Both units are well made and have much-appreciated altitude and temperature features. The BC2006 MHR has an excellent display, especially for cyclists who must use prescription lenses (LARGE characters on display). Typical, poorly written instruction manual omits much in the way of explanation of the feature set. My biggest gripe has to do with mounting the computer and transmitter, both of which rely on o-rings. The Ciclo also used this system - don't the Germans know about zip-ties??? The BC2006 package shipped with an adapter for the transmitter that allows for attaching with two zip-ties, but the adapter (as described in a previous review) has a lip that extends into the spokes of the front wheel, making it virtually useless. It does not work on either of my two bikes/forks/wheel sets. Did these guys actually do any trials with this adapter before shipping it to dealers? Apparently not - it is AWFUL. If you feel confident about relying on a large rubber band for securing your $100 computer to your bike, good for you. I do not. It's a no-brainer as to whether an o-ring (not very durable and you lose your computer or transmitter if one breaks) versus the simple 2 zip-tie system everyone else in the world uses (more durable and if one breaks you keep your investment) is more reliable. I would have given this computer another star and a half if it wasn't for this design stupidity. It would have also been an easy addition to the feature set to include heart rate zone information, even if it meant losing a couple of other outputs (like time up/down and distance up/down). I am going to attempt using wire or other material to reinforce the o-rings, unless someone has figured out a better way of attaching the components to the frame. Finally, I've heard battery life is really bad, but I don't have enough ride time to comment on this. 3 stars

I thought this product was a good fit for my needs - an inexpensive wireless heartrate/speedometer. As it turns out, the directions for setting the unit were very difficult to follow and then the heart rate monitor stopped working within one week. now the battery is running low after about a month. I would have been much better off spending a few extra dollars up front to avoid the frustration and battery costs, not to mention that i now have a unit that doesn't function as a heartrate monitor. very disappointing. the upside is you get to learn from my mistake rather than making it for yourself. 1 star

I used this imitation of bicycle computer for a little more than a month with terrible results it just never work, I really do not have words to describe this nusty mistake I made buying it. I finally replace it with a real computer that cost me about $25.00 dollars a cateye by the way this nusty product (the sigma) cost me $120.00 dollars sorry I do no give it not even a star. it end at trash can. 1 star

If you stop to talk to friends this bike computer will lock up and get in a state that no longer registers speed. The only way to reset it is to take it out of the mount and put it back in, not very safe when you're trying to ride along. The rubber band mounts did not fill me with confidence and I came back to my garage one day to find the sensor on the ground. good job that didn't happen on a ride. The provided bands are not big enough to go around mtb suspension forks. Try a VDO MC1.0 Wired Cycle Computer instead it's much better (but no Heart Rate Monitor). 1 star