Can I install apps on iPhone/iPad from iTunes without syncing?
You can try the install with iPhone Configuration Utility:

http://developer.apple.com/library/ios/featuredarticles/FA_iPhone_Configuration_Utility/Introduction/Introduction.html

http://developer.apple.com/library/ios/featuredarticles/FA_Wireless_Enterprise_App_Distribution/FA_Wireless_Enterprise_App_Distribution.pdf