I think the OP makes a valid point. The seemingly next step to car computing is going to be a device that can go with you everywhere, and do everything. I mean eventually all these devices are going to have to become one universal device with attachments to achieve different things vs a different device for every job.
I could see having a device the size of a moto droid/iPod and a different inexpensive dock for different jobs. A desktop dock with keyboard/mouse/LCD/nic-wifi/USB/Firewire/etc. A car dock with radio/OBD/antenna connectivity. A portable dock w/LCD screen and smaller laptop keyboard for use in hotels or coffee shops (a dock that looks like a netbook maybe, just drop the device inside it somewhere). A waterproof dock w/sunlight readable LCD and waterproof keyboard for the beach or boating.
It's gotta be the future... aye? Some way to consolidate all your devices into one device, not have to worry about data syncing across devices.