I've opened this topic to discuss the question Reuben asked on the 3.2 beta thread regarding the abiltiy to use the Pixhawk to control a 3 volt relay.
My feeling is that you can use the circuit that Marco proposed on the "Using AUX pins as relays for CHDK" thread with a few changes. The spec sheet for the relay that Reuben has lists a coil resistance of somewhere between 25 and 60 ohms depending upon the model of the relay, so the maximum current using a 3.3 volt supply would be 132ma. That is within the range of the 2N3906 in Marco's circuit. So a circuit that looks like the following should work for him. Any other suggestions?