Over the years, I've seen a lot of parking apps that let you drop a pin at your parking space, and then you can navigate back to the marker when it is time to return to your vehicle. iParked (free) does those apps one better, and definitely gets my "gee, I wish I'd thought of this" award for the week.
You launch iParked before you leave for your destination and will see your location on a moving map. When you come to a stop sign or a traffic light, the app drops a marker. If you start up again, marker is picked up. The app leverages your iPhone's motion tracking sensors and GPS.
I tried the app recently when I went out to lunch. iParked did drop a marker at every stop, but when I finally got out of my car to walk to the restaurant, the marker stayed with my car while a blue dot showed my current position. The app runs in the background so you can do whatever else you do with your phone and not lose your parking place.