Not going to say impossible, very few things are impossible with Linux and a determined geek. But very hard. Your problem is the Blackberry bluetooth is not based on the BT HID profile. I think it is based on the SPP profile but I could be wrong.

So basically you would have to figure out the blackberry interface and then build a Linux driver. If it is the spp profile it would not be too hard but certainly not worth the $30 price difference for a real stowaway keyboard (I saw them at Fry's for $129.).

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David