This new Cydia tweak allows you to download, trim, and assign a specific video to use for your ringtone. Jeff at iDownloadBlog didn't have any startup lag when receiving a call on his iPhone 4. I'm not completely done testing this tweak, but so far it seems to be a unique and interesting novelty for your iPhone when you have an incoming call.
Check out video review by Jeff at JailbreakMovies on Youtube:
VUZIQ (4.5MB) is available for FREE from the BigBoss repo in Cydia. Video phone call settings are done in the VUZIQ icon added to your springboard.