SRS Warning Light, Air Bag Off, and low gas indicator flashing

Very scary incident....parked the car, when wife got back in, got the big exclamation point, SRS warning light, brake off light, airbag off light and most weird the single gas bar flashing when, in fact, I had about 3/4 of a tank. The first part of the problem was that when my keys are in the same pocket as my cell phone, there is interference, so I took the keys out, but the same alarms came on. After playing around with it for a while, including locking and unlocking doors with the remote, it finally started, everything normal, including showing gas just fine. I am original owner, so no accidents. I had just put a heavy object in the trunk, maybe it twisted some wiring? I took it out when I got home.

 

Thank you. Excuse the stupid question but is that the primary battery in the trunk, or is there another battery as well? It's been working fine since I posted, with the proper number of battery bars, but the airbag alarm light stays on for maybe 6 seconds after I turn on the ignition before going out....anything to be concerned about?