As far as I can tell there aren't any queries in the script to directly get the impact values from the solvers.
If you're wondering about the math, RigidBodies generally use inelastic collisions formulas, where the masses exchange velocities along a collision normal. There's a so so article on it here at Gamasutra: http://www.gamasutra.com/view/feature/131424/pool_hall_lessons_fast_accurate_.php?page=3
A possible solution to your problem that may be worth testing is just monitoring the length (magnitude) of the velocity vector of your chosen object. After a collision compare the difference in length. If it loses force it's velocity magnitude should shrink, if it gains force, then the magnitude will grow.
Depending on the frame timing, the difference between the current and previous velocity magnitude might answer that question.