This app is free and a lot of fun! The reviews weren’t that great, but I love the potty dance. We’ve mostly used the app for the cheering, and I suspect whether it reminds you is dependent on the version of iOS you have – but for the price it’s worth giving it a try.
(Note: some of the iOS versions don’t allow apps to run in the background – if you are on one of those you would need the app on all the time for it to work)
Check it out at: Pull Ups iGo Potty