iPhoto/Aperture: allocating star ratings during slideshow?

A question/suggestion rather than a problem. Often I do a slideshow of my best/favourite photos to double check the selection. What I'd really like is a gadget in my hand that I could press with a brill! flag or the 1-5 star ratings.

I know I can do this in iPhoto with the keyboard during the slideshow, not sure yet about Aperture. But I want to sit 3 feet back with no visual peripherals onscreen to interfere with the effect of the photo and see its impact from afar (i.e. slideshow, not just normal display).

Anyone know if it's possible? or in the offing? I'd design a gadget myself if I had the knowledge. I've rummaged online but found nothing. I visualise a remote with maybe buttons 1-5 or some similar trigger.
thanks.
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24" iMac, OS 10.5.7, iPhoto '08, Aperture 2.1.4

I guess! . wonder what's the smallest I can find... pea sized would be good, to match my brain.

Even better, thanks pit29, your reply set me off on a different track.
What I've found online and am hopeful about is a wireless keyPAD not keyBOARD, small and with numbers, all I want really. I didn't know they did them (I live neither online nor in a developed country). Bit of a waste of intended use p'haps, but I'm not complaining.
Be interesting to see if it works.