I remember seeing a post on HN from a user that developed one (although I think it was for the web and not mobile). It's the first thing that popped into my head, and I assume there must be similar mobile applications, but I never looked into it. I think it's an interesting concept though, it's nice to choose your best photos when representing yourself online, and in the past I've thought certain photos were great, but friends or family had a completely different perspective.

A nice addition would be to sort the votes by gender and age, so you could see women voted for this particular image, men voted for this one, etc. It might help you find which photos appeal to the audience and age group you're trying to target. This way if you're a 30 something man, you don't have 15 year old girls choosing your clothes and hairstyle.