The Polyend Perc system of MIDI-connected drum beaters might make your human drummer nervous: First, set the beaters up in precise proximity to your drums, cymbals, and percussion; then feed MIDI (or CV) information into them. The MIDI can come from any source: computer software, hardware sequencer, MPC pads, iOS app, etc. The Polyend Perc robotic beaters then play the MIDI beats with exact attention to timing and velocity, so you can get a dynamically varied beat. The mechanical devices are accurate to 1,200 BPM. And you’ll never find them crashing on your couch. Options start at around $900; polyend.com.