A lot of the imaging market appears to come from security/defense applications, either in portal-monitoring or for IED detection. There are defense contractors working on both. The former is easily spoofed (put your uranium pit in a styrofoam sphere in a truck full of grain, done), and the latter is hard to do at speed in a rugged environment.
I've spent a lot of time trying to figure out how to do gravitational imaging on the sub-meter scale, and while it does work, it's hard to get sufficient image resolution to be useful for anything other than a party trick.
If our other science weren't more interesting, I'd be doing it for fun alone. Burning 3-6 months on the project to assess feasibility was as far as I wanted to go without a clear exit strategy.
Generally speaking, though, accuracy of the sensor is rarely the limiting factor in gravity surveys.
For land-surveys, it's precisely knowing your elevation, correcting for the "unwanted" mass distribution around you, etc. For mobile surveys, it's correcting for the acceleration of whatever vessel the instrument is on. Any ideas you might have for improving the state of the art for the mobile case would probably be _very_ marketable.
On a separate note, though, the inverse problem, while fundementally very non-unique, is still solvable for many practical problems (e.g. we know the range of density of the materials involved and we can make a reasonable starting guess for the distribution of mass). Regardless, you're usually interested in distinguishing between a few scenarios that can be easily forward-modeled.