I do a few things much like you. I have a bowl by the door where my wallet, my keys and my sunglasses go. ALWAYS.

If I have to take something with me "tomorrow", I lay it down in front of the door so I have to step over it to forget it.

For pills, which I take 3 times a day, I have an alarm with an mp3 as the alert tone that says "Time to take pills." It beeps at the set times.

I have not had the lost car problem yet, but I never go to places like malls with many entrances and exits. If it were to become an issue, I would just leave myself a voice mail saying "You are parked outside Sears 12 cars deep."

For everything else, Google Calendar is your friend. Tomorrow, for example, I have to go check out a guy's printing problem at 10, be home for a plumbing job estimate at 2, meet a friend at 6 to give him something on my "legacy gift list", and do an airport pickup at 9pm. They are all in Google Calendar and I will get a reminder 30 minutes before each event. Technology today helps a lot. Tommorrow at the airport I will type in a memo saying "Blue concourse, lower level, 3rd row" or wherever I park.