I haven't got a policy in place at the moment but I have considered it in the past. However, 99% of regulars are exactly that, regular, and if one of them occasionally slips up then these are the very people who I think deserve to be let off the hook. (I use a telephone reminder for 2 of my elderly forgetful ladies and we never have a problem now.)
I find the more common type of no-show is one who is a first time client anyway, and in my experience you never hear of them again, so how can you get money out of them for not turning up in the first place?
I find I get about 1 no-show every 5/6 months so it's not something I think about much. Maybe in a salon situation having a notice up saying that a fee will be charged would help people to keep their appointments, I don't know. But it would certainly be worth a try if it was a big issue.