Duper/looper, by Ryota Kuwakubo (the creator of Bitman and BlockJam among others), is a simple drum machine. You put it on a table and knock on the table: the device detects the knock through a shock sensor in the bottom, copies and repeats it till you hold the hammer to stop it.
Louise Klinker and Andy Huntington ‘s TapTap rhythm machine is a system of rhythmic knock boxes.
Each box has its own memory and as you tap on its top, the box waits for a few seconds and then taps back what it has heard.
Add another box, and another, and another, to create longer and more complex rhythm lines as the patterns tumble down the resulting pyramids.
By tapping for longer than the delay period you play a duet with the box as it repeats your earlier rhythms.