I have been using Beddit, B1 and Peak (concomitantly) for a while and all 3 give HR values for my sleep.
Beddit is by far the most crappy, with a value every few minutes at best, but regularly with data missing for part of the night (while sleep data are still recorded).
B1 and Peak give me a data point every 1 minute and have few gaps, but that depends almost entirely on how tight I strap them on.
When comparing the data from all 3 devices my resting HR is very close (usually between 43 and 46). Beddit doesn't give me any good data on how that's changing through the night.
But B1 and Peak provide very refined data, where I can clearly see short HR increases, on both devices at the same time. Unfortunately the values can be VERY different between both (going to 60 on one and 130 on the other).
So in short Beddit will do the rough job, with values similar to other devices, but might failed on some nights.