This is the MiTAC Mio A501Digi-Walker, a Pocket PC Phone with GPS running the Windows Mobile 5 for PPCPE AKU 3.5 OS.
The MiTAC Mio A501 is powered by a TI OMAP 850 201MHz processor, 64MB RAM, 128MB ROM. It has a 2.7-inch QVGA LCD display, a 1.9 Megapixel camera, quad-band GSM, SiRFstar III GPS chip, Bluetooth and a SDIO/MMC slot.