Luckily for you, I've figured out a way to actually control your Sonos system with your PlayBook!!!
The trick is to take advantage of the PlayBook's awesome web browser, leverage remote PC system, and use the Sonos Desktop Controller. This way you will be able to basically control your PC running the Sonos Desktop Controller! Here are the steps to do this so you can control your Sonos system from your PlayBook
Step 1: Install the Sonos Desktop Controller on your PC or Mac.
Step 2: Install Remote PC Software & Complete Registration.
I personally use LogMeIn, as I find the fidelity a bit better than other options.
Step 3: Access your PC from your BlackBerry Browser by going to LogMeIn.com and log in.
Now just type in your ID & Passwords, and you are all set!
Of course you can do a lot more than just use Sonos with LogMeIn but for me, this was what I was really looking for! You will need to change the resolution a little bit and play with some of the settings to optimize it for your PlayBook, but it is pretty cool and now you can control your Sonos system from your PlayBook!