I've been vaguely thinking that someone should make an electronic version of this for a while (I think I might have seen it suggested somewhere else on LW as well?) - a Givewell iphone app, so that when someone on the street asks you for money, you can immediately, there and then, donate it to a more worthy cause, while you're still feeling guilty about not giving money to the homeless person who was only going to spend it on alcohol anyway.

I doubt this would be too much work for someone with any experience, but I have no knowledge of writing iphone Apps and no Mac - is there someone out there with the means and the will to actually do it?