Android users all seem to throw about that it’s an open architecture, but it quite simply isn’t. In order to do everything on an Android phone you have to root it, which is the same as jailbreaking it. Motorola has taken the extreme measure of making sure that if it gets rooted, it’ll completely fuck [...]

Unexpected deviations in gravity are indicative of differences in density. If you point your detector (a gravity gradiometer) in that direction, you can tell what kind of structure is underground. Lockheed Martin is calling this the GATE (Gravity Anomaly for Tunnel Exposure) programme. Using Gravity to Detect Underground Threats | Lockheed Martin.