I'm a runner in my spare time and like to train pretty hard for a good time, but I'm currently injured, which is annoying. Most of the sports watches now do the sort of thing you are looking for.

I've never had any weight issues, so can't really comment on your motivations and what you need. However, I do find that the mount of information they give gets a bit of overload, TMI, if you know what I mean.

My advise would be that you don't really need to use a gadget to loose weight and if you do use one you'll just become obsessed with the stats. Far better to find something you enjoy doing and do that rather than thinking "I need to do x thousand steps today". In your day to day life, if you can avoid driving then walk or cycle, it's much cheaper, then when you do always, always park at the far end of the parking lot. Never take escalators if there are stairs. Lots of small changes to your lifestyle are better than big changes.