I used to run on a treadmill while working in Bangladesh and during a 30 minute run it would stop at least once due to a power failure. There is nothing like the thrill of running on a treadmill knowing it could stop at any second. It should be an extreme sport....... After much complaining from me they put the treadmill on a UPS/power backup device thingy.
I have used a Polar 625 and a Polar R800SD both with foot pods and I think they are brilliant and I think personally they are very accurate for distance & speed. I do not leave my house for a run without it. They are both great heart rate monitors as well. I used a Garmin 305 for a while and found the heart rate function to be lacking but had no complaints about signal or the distance/speed functions. Hope this helps.