JeffQ:
actually, it is for running inside the pipe underground. So any device can do this?
Laying a power cable and a beacon every 40 meters isn't going to be cheap. If the pipe is curved then you'll need more so there will always be line of sight to at least one beacon.
The cabling and the boxes to house the beacons will probably cost 100x more than the electronics inside.
I doubt this is a new idea. Perhaps see what the mining companies use for vehicle tracking and adapt that to your own needs.