Surveying underground tunnels is time consuming and expensive. Automating this process using drones faces similar problems because of personnel requirements to both operate the drone and retrieve it if it becomes stuck in a confined space.
Tumblewheel is a stabilised survey platform within a wheel (of varying width - it may even be a sphere) which can increase of decrease in size and free itself if stuck. It's design is such that it can travel over most surfaces, including water.
It has enough onboard intelligence and sensors to determine if a route is blocked, and to return to it's start location. It's payload can be varied and could include sensors for video/stills/audio, gas, LIDAR et al.
It would create a geo-referenced map - it could even deploy beacons - to which other data can be attributed.
It has the potential to be cheap enough that many can be deployed simultaneously, operating autonomously. If they become stuck they could be abandoned or retrieved collectively to reduce labour costs.