This is a very timely question as only a week ago a device was announced that fits perfectly: the HP iPAQ hw6515 Mobile Messenger.
It has GPS navigation, Bluetooth, infrared and quad-band GSM/GPRS/EDGE for voice and data. There is a built-in QWERTY keyboard similar to the Treo 650's for thumb-typing messages and it comes with handheld versions of Word, Excel, Internet Explorer and Windows Media Player 10. The only notable omission from the hw6515's list of connectivity options is wireless LAN.
For a RRP of AU$1199, you get Microsoft's Windows Mobile 2003 Second Edition operating system, a touch sensitive 65K colour 3-inch TFT display, 1.3-megapixel camera, SD and MiniSD card slots, 64MB of RAM, and up to 56MB of user accessible memory.
In Australia, users also get one-month free subscription to Whereis Navigator.
We are expecting a review unit any day now so check back soon for our full review.