When I proposed to my now wife, I built a reverse geocache box. It had a one way mirror on the top and button on the top. It showed you how far you were and what direction you needed to move towards. It took us to various locations where we had gone on notable dates. Once we got to a particularly scenic hill side, it unlocked and the ring was inside with some roommates hiding in the bushes with a DSLR.
There was just one minor hiccup, I taught my roommates some rudimentary C and gave them a list of GPS coordinates they could pick from. The idea was that I wouldn't even know where we were going. However, they made a mistake and skipped an index in the array, leaving it as zeroed out data. We pressed the button and it listed the next location as 3000 miles away to the East. Luckily, I somehow had the foresight to install a reed switch in one of the corners. I grabbed a magnet from the car and skipped that landmark, breathing a sight of relief.
I have lots of good memories of drawing and sketching a secret project I titled RGCP (reverse geocache proposal) on the floor of my crappy apartment while she looked over my shoulder, trying to figure out what I was working on.
From a technical standpoint, it was a Teensy2.1 with a GPS serial module a SPI LED screen, and a servo for the latch.
https://hackaday.io/project/9449-reverse-geocache-proposal