Watch out for the retraction, it's dangerous.
Making A Tape Measure Gun That Automatically Deploys

This is a video of maker of marginally useful things Uri Tuchman constructing an auto-deploying tape measure. That’s neat. What would be even neater is if it were a voice-activated SMART tape measure. “Tape measure, give me 4-feet 5-inches!” Yeah…that would really be something.