We believe that many Blackberry holders are using the ID Credit Card case manufactured by Case-Mate. The functional case has been brought to Google Nexus One by them.
Same as the id credit card case on Blackberry, the Google Nexus One Credit Card Case adopts slim design, and comes with an ultra slim slot for your ID, credit card or other cards. And moreover, the Google Nexus One case includes ez-slide™ protective film and screen protection kit to effectively keep Google Nexus One from scratches and dust.
The Google Nexus One case is available in two colors, including metallic silver and black. The pricing is $29.99 USD. If needed, you can get more details or purchase it at Case-Mate.