I tried using a wrist mounted computer and found that it got in the way an awful lot, especially when I was lobstering. I kept banging it into things and getting it scratched up. I switched to a retractor specifically designed for the computer (keeps the unit very close to me). I've clipped the retractor right over my heart, and have no problems finding it in zero vis situations.
I have my spg on a breakaway bungie on my left hip D-ring. It is positioned so that I can look down towards my fins and read the guage. It on a break away bungie instead of a clip to avoid entanglements (especially helpful if pulling youself through a narrow opening in a wreck in search of more lobsters!!). BTW -- my compass stays on the surface for almost all of my dives. Natural natvigation has worked quite well for me on wrecks and reefs. Safe diving everyone!