The tiny pager motors (VPM2 from Solarbotics) work great with the USB-1024HLS. I can drive them with the 15mA source capacity of the USB-1024HLS. Using duty-cycle modulation I can control the strength of the vibration. The 4-wire cable I used for each set of 3 is too stiff allowing vibration to couple from one to the next. I'm going to switch to long flexible pairs stripped from a flat cable. That should allow more freedom in placement and less coupling.