We have build an enterprise iPad App and now we want to give it to our employees. Initially when testing, we used ad-hoc distribution collecting all the test device\'s UDID
Probably the best way to distribute your enterprise mobile app and then securely manage users, groups, data and devices is using a Mobile Device Manager (MDM) tool suite.
iOS provides specific APIs that support enterprise deployment via MDM products with API level features like Per App VPN connections that allow you to firewall a DMZ application server to only connect to a specific signed client iOS app. The vendors also provided authentication SSO integration and encrypted storage on the devices to sandbox your enterprise apps from other untrusted personal apps on a BYOD device.
Here's the Gartner 2013 review of MDM products:
The 3 major players are now: Air Watch, Mobile Iron and Citrix XenMobile.
NOTE: I don't work for or have a vested interest in any MDM vendor.