Bluetooth GPS uses SPP (serial port profile), but Ipod Touch / Iphone / Ipad only support HFP (Hands-Free Profile). Natively, Apple does not provide SPP to connect an external bluetooth GPS.
To connect a External bluetooth GPS receiver, You may have to “Jailbreak” the Ipod Touch / Iphone / Ipad.
(We don’t taking any responsibility of your device “Jailbreak”. You might need to take your own risk. )
After that, use the application “Roqy” to connect external bluetooth GPS antenna to your iPad/iPhone. For detail, please refer to http://www.roqy-bluetooth.net/wp/
We have a few screenshot for your info.
Bluetooth GPS receiver can be purchased from gpswebshop.com