You are correct, it is 'Code Signing Identity'.
I have all of mine set for 'Any iOS SDK'.
And I just checked the v1088 iOS Template I uploaded. It doesn't have 'Simulator' under 'Code Signing Identity'. It ran okay under the simulator and then I got the "The application does not have a valid signature." error when I tried to run it on my iPad. It ran before I did it on the simulator.
So, I closed Xcode completely, manually deleted the Build directory in the project, rebooted my iPad, made sure the template was uninstalled on the iPad, started up Xcode and it ran fine.
Then I ran it on the Simulator, cleaned the project and ran it on my iPad again with no problems.
It's a weird ordering thing.
I finally figured out how to add the Simulator configuration. Totally non-obvious.
So I then tried everything with the iPhone simulator and my iPod Touch (using the same sim version as my iPod Touch). Initial run on Sim okay, clean and fail to run on iPod Touch. Shut all down, delete directory and repeat runs. And it was all fine again.
Cheers,
Ancient Lady
AGK Community Tester and AppGameKit Master