One excellent backup check is paying attention to everything that is being said on the frequency to help your overall situational awareness.
I once had been cleared & was rolling for takeoff at a regional air carrier airport during a very busy time; the tower controller then cleared a Cessna into position & hold on an intersecting runway, the Cessna read back "cleared for takeoff" but the busy controller failed to correct him and went on with futher transmiussions. I sort of assumed the Cessna was a training flight and the instructer on board would problably correct the student's error, but as I departed kept an eye on the situation anyway. The controller then requestee I make an early turnout and cleared an air carrier to depart on my runway; glancing back I saw the Cessna was indeed rolling rather than holding and squeezed in a quick "conflict...traffic rolling on (runway)" call. The controller took in the situation, canceled the air carrier's clearance, the jet jammed on the brakes and its pilot started berating the poor controller. Had the air carrier been paying attention to what was going on he too might have noted the same descrepancy and verified things for himself, saving an abort and taxi back.
Humans make mistakes, layered checks and safeguards are our best defense.