SMS to myself
I've used different "todo" apps on my phone, but at the end the problem was: I only visited the "todo" app when I wanted to insert new items, but I rarely watched the list otherwise.
Result: you inconsciously know that the items you'll add in this app will be rarely viewed, and so after a few weeks, you give up using it.
It might seem like a bad method, but sending a SMS to yourself has one major advantage: if you often send text messages to people, you will see your own message in the Messages list, so you cannot forget about it.
- any SMS sent to yourself will be often seen in your Message list, so you cannot forget it
- not good at all if you have many items