The ones I've played around with are basically just GPS markers plus a maps or directional arrow or some sort of navigational aid from "where I am now" to "where I was when I parked the car". I mostly use them (or, more often, wish I had used them) when I park on the street in an unfamiliar neighborhood/city.

Well, if you're in a giant parking lot?

I can't think of the last time I've been in a giant parking lot that doesn't have section markers or numbered spaces. I just take pictures of those, making sure to delete them when I'm done.

Or on some side-street blocks away from your destination?

My camera still works.

That's what's less thinking for me, since if it's so dark my camera can't work, I'm not sure I want to park there. But, as noted, I might not have GPS or cell reception. Those apps wouldn't work in my office parking, for instance. Camera still does.

Okay, to be *totally* honest, I usually write down what every the identifier is onto the parking ticket in a metered lot. But when that's not an issue, camera.

at the airport, I usually stand at the rear of my car and take pictures from 3 or 4 different angles (eye-line), including row/section number and immovable landmarks. Even armed with this, I still run around looking for my car.

I have never thought to GPS mark my car. Maybe the next time I go to Disneyland...

the real annoying way to find your car... hit the PANIC button on your door unlock clicker. If you are in range, you get flashing lights and honking horn. Folks do that at Angels Stadium all the time at the end of the game. Nothing worse than walking right past a car as it goes off and scares the beejeebees out of you.

I figured out I was looking on the wrong floor of a parking garage that way once. I was very nearly convinced it had been stolen.

Heh, don't have a keychain fob. Looks like Parking Genie just drops a pin onto Google Maps, its only advantage over just doing that directly is that it stores parking locations in one spot. Eh.

And it appears that most of the other apps I thought I had were WebOS.

How can you tell which floor you're on with GPS?

GPS can return altitude info as well, assuming you have GPS reception in a parking garage. But I don't ever recall seeing altitude info displayed in a consumer GPS device, except maybe those for hiking.

Locale support told me they couldn't tell me which floor I was on, ground vs. 11, so I wondered how it would work in a parking garage.

Ha, our phone GPS once freaked out on us. We followed its directions and drove into an abandoned parking lot. It said, good job, well done, you are now on the interstate. We were all, uh... And we were! Just directly underneath the relevant ramp. We just couldn't tell because of the surrounding buildings. So we drove out, and around, completely confusing the GPS, and then were fine. It was pretty funny, though.