We have managed to achieve this, It is via the limations box but we done all the work for you . by doing the following.
1. Goto banner you do not want on mobile site.
2. Goto delivery options and add the following limitation: Client - Useragent
3. Add this value: /Mobile|iP(hone|od|ad)|Android|BlackBerry|IEMobile|Kindle|NetFront|Silk-Accelerated|(hpw|web)OS|Fennec|Minimo|Opera M(obi|ini)|Blazer|Dolfin|Dolphin|Skyfire|Zune/ This will cover 98% of mobile users. Enter it exactly how it is above even with / at the beginning and end. The remaining 2% will be mobile users that have pre historic OS so any website built after 2004 wouldnt load of this type of device anyways so no worries in covering them.
4. Delete certain cache files to make change's instant or wait 20mins.
Location of cache files: var/cache
Files to remove: anything that starts with deliverycache_
It would be great to have http://mobiledetect.net/ integrated with Revive-Adserver.
I have to hand-code a very basic way to show narrower banners in mobile than in desktop. I reckon that the huge majority of Revive users would be happy to see such feature. Even as a paid plugin.
We could have several banner sizes per zone to cater for all screen sizes, Retina for iOS, etc.