Finally! An free one!
While I do understand that developers need to get money too, I don't think that they should charge money for using someone else's (parrothd) work and simply developing a GUI for it. I'd be happy to donate to people, but I don't think they should make money mandatory.
Thanks a bunch for this app and I hope your app becomes widely used! I'm probably going to use it's source as an example for one of my projects (which is going to be free and probably open source as well)
EDIT: Quick question: Does this automatically turn WiFi off when starting tethering? Also, you should come up with a more creative name ;-P