There was a tool named "droplet". maybe google can find it. The dropper (a sandbox is something completely diffrent IMHO) that is part of my engine won't help you a lot since the engine is not open source, tho the map description format could be used by other engines as well. However, it's not freeware.
I'd suggest to search the forums for the term "dropper".
I'd suggest to search the forums for the term "dropper".