At a press conference at its Californian headquarters Google has finally made the Nexus One Android phone officially official, having previously confirmed the mobile's existence.

Google explains the launch of the device, which it says it worked very closely with HTC to create, as part of a plan "to bring devices to the market that are going to help showcase very quickly the technology we're working on at Google".

This makes the 11.5mm thin Nexus One an important device for Google, offering flagship specs and performance for the Android platform.

Those high-end specs come in with the 1GHz Snapdragon processor from Qualcomm (previously seen in the Windows Mobile TG01 and HD2 as well as in the just announced Lenovo Skylight) as well as a 3.7-inch AMOLED display and the 2.1, or Eclair, build of the OS.

Features include HSDPA, Wi-Fi, a 5-megapixel camera, compass and GPS, stereo Bluetooth, 3.5mm headphone jack, noise reduction tech for calls, the option of two lines of engraving on the back, a 4GB microSD card expandable to 32GB, sensors galore with a light and proximity sensor as well as an accelerometer and a multicolour LED-backlit trackball.

As had been rumoured, the Nexus One is to be offered on a SIM-free, handset only basis in select markets for $529. This price will include a wall charger, USB cable and free shipping in the US. Google will also ship the unlocked version of the phone to the United Kingdom, Singapore, and Hong Kong at launch for those with a Google Checkout account.

It seems from the now-live product page that Google will also offer the device on contract through both T-Mobile (with the handset cost confirmed as $179) and Verizon Wireless in the US, but details of plans are still to be confirmed. 

More exciting for those on the UK side of the pond, Vodafone is to offer the Nexus One in Europe, so presumably including the UK, from the rather ambiguous "spring 2010". We will keep you posted.