Often, I'm in a situation where I need to remember to do something without being able to write it down.
Example: While changing diapers, you notice that the used diaper bin is almost full. You make a mental note to replace it. You cannot make a written note, because you haven't washed your hands yet and the baby might fall off the changing table. Of course, as soon as you are done and the baby is dressed again, you have forgotten about the mental note. Repeat until the diaper bin is actually full and you have a problem.
How do I fix this? Are there techniques to "set a mental timer" to go off in 5 minutes? Or are there other smart ways of taking notes when you cannot use your hands at the moment?