Can't wait to grab a lot of these when they're available:

http://www.seeedstudio.com/wiki/DevDuino_Sensor_Node_V2.0_(ATmega_328)

Things seem to work with the mega 2560 after realising that it has completely different SPI pins:

pin D8-----------CE (chip enable in)
SS pin D53----------CSN (chip select in)
SCK pin D52----------SCK (SPI clock in)
MOSI pin D51----------SDI (SPI Data in)
MISO pin D50----------SDO (SPI data out)

In the sketch I use this:
Gateway gw(8, 53, INCLUSION_MODE_TIME, INCLUSION_MODE_PIN, 6, 5, 4);

Dunno why the pro mini 5V is not working, but as I'm able to talk to a sensor already I probably won't dig further into that..

2;0;1;0;26.1