LX Navigation also produces what look to be good units in the AHRS field.

http://www.lxnavigation.com/iris-efis/

You can get either a 2 1/4 (57 mm) or 3 1/8 (80 mm) size for 990 Euro and 1090 Euro respectively.

These are completely stand-alone units with a back-up battery

They provide:
- a speed tape showing IAS, TAS and ground speed
- altitude tape also showing climb/descent rate
- heading indicator
- bearing to a selected destination
- QNH setting

All of these display options are user customizable to show as much or as little as you wish on the screen.

The full user manual can be downloaded here with all the details.

http://lxnavigation.com/downloads/manuals/LX_HUM_R1.pdf