Thanks, I'll take a look, although it looks as though I'll have to give up on the idea of using FreeBSD on my RPi-B with its Piface Digital interface because there are too many obstacles to getting it working.
I'll probably try out a few of the examples on my RPi2.
I think the 7 dollar relay card aragats recommended is spot on. it has relays and LEDs. Really simple to show on off.
With specialty Hats or Capes you really need to check to see if base chip driver is present on FreeBSD.
Then you got to deal with making a custom DTB/DTS or modding the Linux one, if it exists, for the hardware to work.