I have created a mobile app using Phonegap Build (not just Phonegap...but Build). I have a Windows PC and do not use eclipse or xcode. I just write the Javascri
If you want to test on a device, your app needs to be signed using your certificate. You'll also need a development provision profile that includes the device ID's of any devices you want to test on. In order to get those things, you need to join Apple's iOS developer program. This is true even if you're using the PhoneGap Build service; in order to build for a device, you need to upload your certificate and provision profile to PhoneGap Build. Look at PhoneGap Build's Building for iOS page for complete information. All this means that you'll need to pay the $99 fee to join the iOS Developer Program.
An alternative is to jailbreak your device (or, in this case, your friend's device). You can find instructions for that on the web if you're so inclined. However, I don't think you'll be able to build through PhoneGap Build in that case -- you'll need to build your app yourself with Xcode or possibly some other set of tools.