(Updated) Easiest Way:
I have found another way to distribute the ipa.
This website provide service to distribute you adhoc app (ipa).
Another way:
To Distribute your app to other device your have to register those device in your developer account.
To AdHoc distribution you need the devices UDID.... register those in developer account and make a AdHoc profile and sign your app using the profile. After that send the AdHoc profile and your app to the Users...