Looks pretty good actually (from the screenshot), you even have an iPhone app and everything. Why not just charge a small something, even if it's only to get you a nice side income? Somebody mentioned $5/month as a reasonable price for something like this. For me personally that would make me less hesitant to sign up as currently it would seem you could pull the plug any moment. Unless you like the idea of being able to pull the plug at any moment of course, which of course is your prerogative.