If you watch the Boston Marathon next Monday, keep an eye out for Jason Jacobs. He should be pretty easy to spot; he’ll be the one dressed as a giant iPhone.

Jacobs is the founder of FitnessKeeper, Inc. , which sells the RunKeeper iPhone application. RunKeeper uses the iPhone’s built-in GPS to track how far and how fast people run, walk, cycle and whatever. They can then share their numbers wit h friends.

The marathon idea came about after a pitch from some students at Emerson College three weeks ago. In Jacobs’ own words, here’s why he’ll be dressed as an iPhone:

With RunKeeper, we have been really big on “humanizing the brand” (check out @runkeeper on Twitter), and what better way to humanize the brand than to have a giant iPhone with RunKeeper on the screen actually running in the marathon?

We partnered with a team of undergrads in a social media class at Emerson College to help us put together a marketing campaign.  They pitched me on the idea with only 3 weeks before the marathon, and I fell in love with it right away.

We jumped into action immediately.  By the next morning, I had a marathon number (VERY hard to do), and we’ve been scrambling ever since to line up tshirt and other vendors, get the costume built, plan all of the race day logistics, build awareness in the community, etc. etc.  And this is all while training for the race (typically an 18-week ordeal) in 3 weeks time.  Even better is that we have been filming the entire process!

The plan is to launch a series of viral videos leading up to and immediately following the race, which document the prep for this campaign from soup-to-nuts, as well as the outcome.  Think Apprentice meets Real World meets Behind-the-Music.

It’s a great idea, although there’s only one video at the moment and it isn’t exactly viral quality. Jacbos is also raising money for Spaulding Rehabilitation Hospital, which is a worthy cause.

I hope this works. It’s gonna be hot in that iPhone suit!