Once upon a time, there was Wherigo. It was closed-source, closed-format, and worked only on PocketPCs (and some kind of obscure navigation device). It did not work on cellphones and the developers apparently weren't interested in making it work.
Turns out, however, that the Wherigo Builder produces plain Lua source files. It can't be too hard to make that work on a mobile phone, now can it?
Well, let's hope not. Enter matejcik, who just recently bought a bluetooth GPS module to use with his phone. And whose idea of fun is, among other things, staying up late (or early, you might say) coding weird stuff.
Working name of the project is OpenWIG. As of now, it can run nearly all of Zooventure Level Two from the tutorial.
No GPS connectivity yet, but you can input coordinates by hand. I might keep this feature, as it would enable folks without GPS-enabled mobiles to play. Then again, I might not - you know how things go, cheaters are everywhere and this would only make it easier for them.
You can't load your own cartridges yet, and you will probably never be able to load gwc files, as the format is closed and I have no experience in reverse engineering. But once the loading functionality is there, I will probably set up a web service that would take your sources and compile them to OpenWIG-friendly format.
Heart of the midlet is called Kahlua and it is a Lua virtual machine for J2ME. It eats Lua 5.1 bytecode compiled files and works pretty damn well, considering its size. It is also fast enough on all phones I tested.
(Then again, it's not like the Lua scripts in the cartridges do a whole lot of work. Setting variables, conditional branch here and there, that's about it.)
And as an added value, the guy who wrote it was very helpful and the (two) bugs I reported were fixed immediately.
No download link today, but you can find some testing versions in this thread (in Czech).
Update: check out OpenWIG's Google Code page.