You can read this in Haaretz:
Among proposed tunnel-detection technologies is the use of vehicle-mounted, ground-penetrating radar. However, this solution can only detect tunnels to a depth of 10 meters and the last tunnels discovered during the Gaza operation that reached Israeli territory were as much as 25 feet below ground.
You can also read this there:
IDF to test tunnel detection system on Gaza borderIf the system proves it can identify the digging of infiltration tunnels, the military could deploy it within a year.
In this paper, the Jerusalem Post, you can read this today:
IDF successfully tests system designed to detect terror tunnelsSenior army officer says system passed lab tests, currently undergoing field testing; could be deployed around Gaza within 1 year; system will cost at least NIS 1.5 billion.