I've been using the new iPhone apps for truple (best accountability/screenkin) on an old iPhone I have. Dang thing is bulletproof. It is a touch annoying, but so much better than just viewing website domains.
My biggest recommendation is make sure you do the full setup guide. There were a lot of steps, but if you pay attention you'll see why. For example, Best Accountability's final step shows you how to block the settings app to close up loopholes. If you don't do that, using the app is more or less pointless in my opinion.
Super excited to have iPhone as an option now that there is a great iOS accountability solution.