I have tried a few apps with varying success but at the moment I'm using mySugr Diabetes Companion. It's really comprehensive and have found the search functionality really useful. The company is mostly made up of diabetics and you can tell when using it.
Tbh, I've tried a few, but always end up writing them down on a record sheet. If I want to add extra info to the sheet i squeeze it in. just because its easier to spot patterns than looking at loads of different screens.