Put a stack of 3x4 index cards in you back pocket, and write thing down as needed. In the evening, (eg when you pull keys/wallet out of the pocket) review the cards briefly and toss the used once into trash unless you really need to keep one.
This is a low-commitment device that still achieves half the benefits of really writing things down.
This is a low-commitment device that still achieves half the benefits of really writing things down.