The phone can store music and has blue tooth, so why can't you use it to listen to music?
From my own experience, GPS tracking of mileage is not exact at all, so not sure why you'd use it. Its OK if you do so much distance that it doesn't matter, but precision is not great. I know it isn'T because there are several spots I know the exact distance they are from my house. I use runKeeper too.
I run with my iphone strapped (like holding a camera) to my hand. Biggest watch ever ;-).
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It plainly says it plays music independently on the web site, so playing video is a given (really crappy players with almost no storage 10 years ago played videos...). Don't know how much storage it has, but I'm guessing 4G would be an absolute minimum. It can collect data and then sync to the phone. Why would it be dumb, its still a small computer?
I'll wait to see actual specs before commenting further