I use gps4cam on the iPad (it's iPhone only at the moment).
Excellent for what it has to do. Nice and simple UI.
You can export even on QR codes, so that you can geotag Raws too with the free proprietary companion Mac App ( don't remember the windows compatibility).
When returning ack to the Mac I simply send the track log via email and drag the attachment directly onto the lightroom track log import dialog and voila… tagged photos.
Gps4cam has been on my Samsung Galaxy 8.9 tablet (Android OS) for a few months now, so it is not limited to iPhones only. It works flawlessly with Lightroom 4, is super easy to use too. I had a problem the first time I used it, and the support was very fast and efficient. If you download the free app for your windows pc, make sure you download the latest beta version.