iCM12 - usbLink (Smart USB to Serial Converter)
Price
$14.50
usbLink is a USB to Serial Converter which can support UART port (TX/RX), 4x digital IO or 3x 10-bit ADC input.
4x4 Keypad is used to allow user to key in decimal number (0-9), (A-D), * and # keys.
Features:
Dimension:

Photos (with iBoard):
Tutorial: