Our newest product, Servus, has a requirement to control hardware pager systems via RS-232. Since Servus is Android tablet-based, it made perfect sense to use the recently introduced Android Open Accessory Development Kit (ADK) to implement this capability. However, support for the ADK has been a bit slow all-around. This post details what I've found through trial and error thus far.
This one's easy -- use the official Arduino Mega ADK board. I'm successfully programming/testing it on an iMac running Lion without having installed any third-party drivers. I can't say the same for the Freaduino clone board I purchased from China before the official board was available. It's sitting idle in a drawer because I couldn't get it working properly. If you can get your hands on an official Google ADK board, I'm sure that works great too but they appear to be pricey.
I have all the below tablets so this matrix is based on my first-hand experience.
|Tablet||OS Version||USB Port||Synopsis|
|Motorola Xoom||3.2||Micro USB||This tablet works with the ADK.|
|Acer Iconia A500||3.2||Micro USB||This tablet works with the ADK.|
|Acer Iconia A100||3.2||Micro USB||This tablet works with the ADK.|
|ASUS Eee Pad Transfomer TF101||3.2||Proprietary||This tablet works with the ADK.|
|Samsung Galaxy Tab 10.1||3.1||Proprietary||This tablet works with the ADK.|
So, as it stands today, out-of-the-box you can only use any of the above tablets. If you just want to use a phone, I can confirm that the Nexus One works fine with the ADK as well.
Hopefully this information will prove useful to people since I couldn't find definitive (or completely accurate) information anywhere on the web.
Update: Since the Acer Iconia has been updated to 3.2, the ADK now works.