Android: Always being told by your mother that you don't call often enough? Not staying in touch with enough work clients? Nextcall is a simple Android app which ranks your important contacts based on when you last called them, helping ensure you make regular calls to important people.
Within the app, you can identify and categorise the contacts you consider important, so you're not being reminded to call someone that doesn't actually matter that much. You can also schedule reminders for how often you should call individual contacts, or contacts in a set category. The app won't track whether you successfully make contact when you do ring, but if you make a habit of reviewing who you haven't called when you have time to kill, it could be a useful enhancement.
Nextcall is a free download for Android devices. (A premium version is apparently in the works.)
Nextcall [Google Play]