Good news... my dad has an Ipod Touch that he's gonna let me borrow. So I'm gonna test it out a bit with my Freedompop Photon to get an idea of call quality, etc. If it sounds good and works pretty well, I'll bring it along and hopefully will have a decent solution for calling over wifi. BTW: for Google being blocked in Taiwan, I'll probably load up HotSpot Shield or something equivalent and free that can proxy my location through a different country that does allow Google (anyone know of any other good and completely free region-switching/VPN apps for IOS and Android?)

BTW: as far as renting a mifi hotspot in Korea, is there also a 3-day waiting period etc like for sims? Or can you pretty much get one right away? If the latter, I'm wondering if I should just wait till we're there to rent one or if it's best to reserve one ahead of time.

The only thing I'm somewhat concerned about is how much it'll cost my in-laws, with an EG sim, to call my US-based Google Voice number.

There's a table of rates on EG sim's website but it's confusing to me and I don't know how to interpret it:
Nation EGM* R Telco S Telco K Telco
USA 150 720 756 900