GPS over tethering app.
You can use Location information
Even if your iPad not have cellular.
You can use with This app and tethering.
Just start with Route+.
1.Start Personal Hotspot from Your iphone to your iPad.
2.Start this app on iPhone
3.Start Route+ on your iPad.
3.Setting Use TexaGPS on Route+ preference.
Even if your iPad don’t have cellular & GPS,
You can use high level location information automatically.
Continued use of GPS running in the background can dramatically decrease battery life.
===for iPhone Developer ====
Location Tethering API. You can use Free.
http://issho.dht.jp