The reminder tool that's not even an app.
There is something about gongyo that makes me remember things on my to-do list in the quickest of fashions. The amount of times I'm in the middle of gongyo and that thing I was supposed to do, or should do, comes up in my mind like a lightbulb has been turned on. When this happens, it's best to finish gongyo then deal with matters. However, I find it hard not to stop half-way through and attend to whatever it is I've remembered to do. It's like it wakes my brain up.