I think almost any cool or worthy outdoor (out-of-home) idea becomes inherently experiential. This idea puts both HP Printers and selected small or home office business on stage in a vivid demonstration that has show quality.

Every morning the billboard - located in major media market or significant pedestrian point - would begin as a white canvas with the HP logo. Then it comes to life as a series of HP home office printers begin to produce office work sized copies that are gathered and posted to the board by hand by a part cirque, part Peter Parker wall-walker. 

What becomes assembled is a billboard message or logo for a small business or home office operator. It stays up for an hour and then is replaced with the build of an HP themed message. Which after a time is replaced by another small business.

Of course, the process is captured in real-time (and edited) video and incorporated into HP on-line properties. 

For the small businesses featured there's the added bonus of hometown news coverage for being featured in a major market media partnership with the biggest initials in printers.