I tried using a Wakemate (a dedicated bluetooth wristband that talks to a companion iPhone app) and found it to be pretty close to useless for me -- I move around quite a lot when I sleep, and I found it was consistently waking me up within a minute of the start of the wake period.
That doesn't mean that stuff like this isn't useful for normal people who don't flail around like an animal when they sleep, but an anecdote is an anecdote. I'd also imagine a more sophisticated piece of software might be able to learn your sleep pattern and adjust the sensitivity (i.e. calibrate the threshold based on how much you personally move when you sleep, rather than the hypothetical average person).
(in Wakemate's defense, they have an awesome no-questions-asked 30-day return policy, so I was happily able to return it and get my money back when I wasn't satisfied. They were a true pleasure to deal with.)
That doesn't mean that stuff like this isn't useful for normal people who don't flail around like an animal when they sleep, but an anecdote is an anecdote. I'd also imagine a more sophisticated piece of software might be able to learn your sleep pattern and adjust the sensitivity (i.e. calibrate the threshold based on how much you personally move when you sleep, rather than the hypothetical average person).
(in Wakemate's defense, they have an awesome no-questions-asked 30-day return policy, so I was happily able to return it and get my money back when I wasn't satisfied. They were a true pleasure to deal with.)