Miniaturization and weight reduction of existing technology are worthy scientific pursuits.

It’s possible to remote control a cockroach sized bot, so now you can be a sort of “fly on the wall” in any conversation. Drop the roach off by drone which can double up as the access point.

Even spies have hobbies.

You might be able to do some interesting wildlife documentary movies, though.

It could be useful to locate people trapped under rubble after an earthquake.