I think this is still the best system for me. If I kept a PDA or a day calendar to remind me of the few things I need to do on any given day, that would be just one more thing for me to maintain and remember to take with me.
My stepmom was appalled last year when she asked me to bring (of all things) my dad's PDA to him when he was in the hospital. I took out a pen and carefully printed "PDA" on my wrist. She asked me why I was still writing on myself at 28. I tried to explain that this system had worked pretty well for all that time, I'm not a busy person, and I'm not terribly concerned with my personal appearance, so why switch now? Gawd, quit hasslin' me, you don't have to make a federal case of it, I'm going out, just OUT, ok?, you don't run my life, I didn't ask to be born, etc.
She wasn't convinced, but sure enough, I remembered to bring the PDA. And if I don't get to the gift shop, the bank, and the phone store tomorrow, it'll be because I'm lazy, not because I forgot.
Maybe I should just get "TO DO:" tattooed under my left hand. It would cost about as much as a PDA, and it would last forever.