Our club uses the same as Geistware's... and this is the same at other clubs I've flown at.
I believe it to be the best method, short of having a fulltime radio impound officer
You put up your card to get the freq pin. The reason this is so much better than
'putting a pin on the frequency' is that anyone can simply fling your pin into the weeds.
On the "take the pin" method... he who has the pin controls the frequency. No chance of confusion.
Even if they toss your AMA card aside, it doesn't matter... they won't have "the pin".