Originally posted by Eruditass Correct me if I'm wrong, but these are wireless triggers and work on any system. They might, however, support remote shutter, which may only work on Canon/Nikon.
If they're like the RF-602s, then there are two different types of transmitters (Tx), one for Canon, one for Nikon. The difference is due to the different hotshoe pin arrangements, which are required for the wake-up functions on the flashes. You should be able to switch and swap, i.e. Canon Tx on Nikon body, or vice versa, but I'm not 100% sure.
I'd be curious to see what the sync speed these Meike triggers are with the Pentax system though. The RF-602s consistently full sync with Pentax at 1/125th, but at 1/160th and 1/180th, results vary, usually with the shot catching a bit of the trailing shutter curtain. (unless the half-press trick is used). However, from all the reports I have read, the Meike triggers aren't as reliable as the RF-602s; there is an occasional no-fire, whereas with the RF-602s, a lot of people, including myself (I have 1 Canon Tx, 1 Nikon Tx, and 6 Rx), claim 100% reliability.
EDIT: just did a bit of reading, looks like the Meike units have universal Canon/Nikon transmitter units, i.e the same Tx unit can fit Canon or Nikon and still retain the ability to wake-up flashes.