I've never seen a part like this before; from a slightly different angle, you can see that it is labeled "BZ1", and I've never seen anything with that prefix before either. Neither has Google, so maybe one of you knows.
It seems to have only two terminals, though I'm not sure what they're connected to; the routing must be underneath the part. It's mounted on a double-sided PCB, with vias everywhere; some are to the myriad of test pads, some are to the ground plane, some are for actual signal routing; however, there is clearly solder resist between the pads of the component and the ground plane on this side, so I don't suspect either terminal is connected to ground.
This is a DC board. It takes a 24V supply at about 3 Amps, and has an onboard switching + linear regulator combo to bring it down to 3.3V. (I don't know if it pulls off other voltages upstream of the 3.3V LDO.) There is a microcontroller that switches 4 NPN and 4 PNP MOSFETs to control a motor. (Each is rated for 60V and 20A, so I don't know why there are so many.) The power and motor switching circuitry is on the other corner of the board, though; there are mostly digital components on this side (microcontroller, external SRAM, SD coard slot, an I2C device, and some headers for ISP.)
Any help would be appreciated!