I dont' know of any programs for the mac.
For PC's there is
www.photoboof.com software for $75 but you'll also need to use a canon powershot camera, those cost $200 or so and you'll need to buy PSremote software which is PC only too for $50.
I have written my own script using www.autohotkey.com but again this is for PC ONLY. It would work with Nikon capture if I put a little bit of time into rewirting it.
Peace, Rolland
re@rollandelliott.com