Surprises can be wonderful, especially when it comes to taking an existing platform--such as Skype or the iPod Touch--and opening it up to an entirely new set of possibilities.
Voxeo and Vapps have a way to connect Skype into their SIP-based platforms, leveraging the capabilities of Skype to use its wideband G.722.2 codec for higher quality voice calls. It's a little awkward, since connecting into Vapps under G.722.2 apparently requires dialing a rather large (over 99 digits) number within Skype. Read Phoneboy's Skype to SIP Possible, In Use [1] scoop
One might doubt Apple was surprised to find someone had figured out how to turn an iPod Touch into a VoIP phone. Cheers to the lads in the Land Down Under (Well, Lifehacker) for providing step-by-step instructions in how to hack an iPod Touch into a Phone [2].
Links:
[1] http://www.phoneboy.com/2226/skype-to-sip-possible-in-use
[2] http://www.lifehacker.com.au/tips/2008/04/16/turn_your_ipod_touch_into_an_iphone-2.html