Portal Timer is a very simple Android app. It sits in your notification tray and times your ingress portal hack cool down periods. For example, as of this writing, you can only hack a portal once every five minutes. This app keeps track of how long of a cool-down time still remains.
Get the app on Google Play.
Fork, commit, push, and send us a pull request at felixb/portal-timer.
This app is licensed under GPLv3.