Hershenson and Britt were part of the trio that founded Danger in 2000. The third partner: Android chief Andy Rubin. The three engineers launched pioneering consumer smartphones, like the once-ubiquitous-among-celebrities T-Mobile Sidekick in 2000.

Now they’re back together again. Within the last 12 months, Britt and Hershenson quietly joined Google (GOOG) to run a new wing within Android called Android Hardware.  They tell me they spend their days building things that will turn into reference designs for Android peripherals.  Android Hardware is exploring everything from home automation to exercise gaming and robotics.  While there are no immediate plans to build Google-branded Android hardware accessories, Britt indicated that he would love to see Google introduce some of its own Android peripherals in the long term. The folks in Cupertino (AAPL) have to be paying attention.

At Danger, the three were determined to change the mobile industry by putting a tiny computer in everyone’s hands.  They came up with the Hiptop, which was adopted by a renegade mobile carrier Voicestream shortly before that company was bought out by T-Mobile. The Hiptop was rebranded the Sidekick and went on to critical acclaim, at least in its niche of teens and celebrities who loved the ability to text message with a QWERTY keyboard, without having to carry around their father’s BlackBerry. [For an interesting and thorough history of the early days of Danger told by Britt, Rubin and Hershenson, have a look at these videos from a 2004 Stanford talk.]

As Danger grew, investors wanted a manager at the helm, so Rubin relinquished the CEO role. Rubin left Danger in 2003 to form the company that would later become the basis for Android. Google bought Android in 2005, leading to Rubin’s role as Senior VP at the company — one of seven reporting directly to CEO Larry Page — today.

Britt and Hershenson, meanwhile, stayed on at Danger for years, even after Microsoft (MSFT) purchased the company in 2008 and went to work killing the Sidekick.  They briefly moved into the “Pink project,” which produced the ill-fated and short-lived Kin phone (it was killed last summer).  After the Kin’s introduction, Britt and Hershenson both left Microsoft on the same day.

The way Hershenson tells the tale, he drove almost directly out of Microsoft’s parking lot and over to Google’s Building 44, home of the Android team.  Britt wanted to take “a year off”, but says he was lured into Google within months by having lunches at the Google campus and learning what his former colleagues were up to.

At Google, their new roles dictate that the pair spend most of the time in labs, soldering irons in hand, engineering new products and product uses.  In other words, they are back to a version of the rented office space they were tinkering around on robots in with Rubin when they launched Danger back in 2000.

Except today, it’s 2011. Smartphones are mainstream and supremely powerful — it’s not just rappers and Paris Hilton who carry around the state-of-the-art in their pockets.

And unlike with Danger, Britt and Hershenson are involved with a goliath, not an up-and-comer. Android is turning out to be bigger than even the iPhone in terms of market share.  That scale is what attracted and the former Danger founders to get the band back together, with their goal being to build the hardware and features they want to see show up in new Android devices. It’s not enough for Google to just provide Android software to carrier — now they hope to influence what handset makers build, too.

The new prototypes the team engineers at Android Hardware could end up in the hands of hundreds of millions, if not billions of people, which, after all, is what Rubin and the Danger crew were shooting for all along.

In case you were wondering: Britt and Hershenson both carry around Google Nexus S phones, though they’ve tried the new Android Sidekick and love the keyboard, which stayed true to its circa-2000 origins.