This is an Enhanced version of my basic to-do app, which stores to-do items via IndexedDB, and then also aims to provide notifications when to-do item deadlines are up, via the Notification and Vibration APIs.
The IndexedDB and Notification API functionality all works on Firefox desktop, Firefox Android, Firefox OS, Chrome, and IE 10+.
The Vibration API stuff works on Firefox OS and Firefox for Android.
You can try it out live.