Using embedded code that reports hardware, software and GPS location characteristics, Flurry Analytics has detected approximately 50 devices that fit the description of the tablet computers Apple (AAPL) is expected to unveil on Wednesday.

Unlike other Apple prototype devices detected by Flurry’s data-gathering code, these test units never leave the Cupertino campus — consistent with the high-level of secrecy surrounding Steve Jobs’ latest project.

But traces of the devices’ existence stick to the apps their users test. Based on the data it has gathered, Flurry on Sunday issued, with “a fair level of confidence,” these findings:

• Testing of the devices, first spotted in early October, increased dramatically in January
• They are running a special version of the iPhone operating system labeled OS 3.2 (iPhones currently use OS 3.12), not a version of Mac OS X
• Testers have run approximately 200 different pieces of software on the device
• Games are the No. 1 category of software being tested, suggesting that the tablet is intended more for play than for work
• There was no evidences of the kind of industrial apps run on most current tablet computers
• There was a strong trend toward news, books and streaming music and radio, leading Flurry to speculate that the new Apple tablet will “focus heavily on daily media consumption”
• Across all applications detected, there was a “strong theme of sharing and/or social interaction including social games, social networking, photo sharing and utilities like file transfer applications”
• Good news for developers: “from the testing we observed,” writes Flurry, “it appears that Apple wants to leverage the 130,000+ applications already available in the App Store on day one”

All will be revealed on Wednesday at Apple’s “latest creation” event. Tune in here for our live coverage from San Francisco.

You can read Flurry’s full report here: Apple Tablet: The Second Stage Media Booster Rocket.

See also:

• Apple tablet rumor round-up
• Apple Tablet: New details leaked
• Apple tablet: The video previews
• Apple tablet may not ship until June
• Tablet: Big iPhone or thin MacBook?
• 5 reasons iSlate will succeed/fail
• Jobs “extremely happy” with tablet

[Follow Philip Elmer-DeWitt on Twitter @philiped]