Just a colleague threw a link to a curious little thing: ARM S3C2440 Development Board + 3.5 "LCD Touchscreen
cgi.ebay.com/ARM-S3C2440-Development-Board-+-3.5%22-LCD-Touchscreen_W0QQitemZ170279936297QQcmdZViewItemQQimsxZ20081118?IMSfp=TL081118119003r6454(according to the link - more information than under the cut).
It seems to me that, on the basis of such a device, it is possible to develop both a terminal for a wearable computer and a wearable computer / PDA itself - not particularly powerful, but ...

')
SpecificationsProcessor: Samsung S3C2440 (ARM920T core with MMC, frequency up to 532MHz)
SDRAM: 64Mbyte, 32bit, 100MHz
Flash: 64Mbyte Nand Flash + 2Mbyte Nor Flash (BIOS installed)
LCD display support: works with STN LCD displays (2, 256 and 4096 colors; resolutions 160x160, 320x240, 640x480, etc.), and TFT LCD displays (colors - 1, 2, 4, 8 bits per pixel using a color palette , and 16-and 24-bit color; resolution - 160x160, 320x240, 640x480, 1024x768, etc.)
USB: X1 USB host and 1 USB device
Sound: microphone input, stereo output, beeper
Network interfaces: X1 10M Ethernet (RJ-45 connector)
SD / MMC: interface for SD card interface and holder (holder?)
Camera: 20-pin camera interface
UART: 1 RS232 serial port, you can connect up to 3 additional COM ports
Jtag: standard JTAG interface
Buttons: 4 test buttons
LEDs: 4 LEDs
I2C Bus: AT24C08
AD input: AD input test
RTC: RTC (battery backed)
Extensions: 34pin GPIO expansion connector, 44 pin System bus expansion connector
Power supply: + 12V
Dimensions: 120x100 mm
Operating Systems: Linux, Windows CE
Price: $ 139.90
Shipping to Russia: $ 49.90, 6-15 business days