Well, I took apart the iSaddle to see where I could add the switch and then decided that I'd have to remove solder to really get to where I wanted to get. Anyway, I found a dongle that has a built-in power switch already.
It'll be awhile until it gets here though, so for the time being I'll continue to either not care about it being plugged up or unplug it. Just depends on where I am.
In the long run I'm going to search for a more integrated solution. It'll probably be one of the last things I do though as I don't really mind the current setup too much.
I'll post an update when the new unit comes in.