A local Property Manager of a high-end apartment community has requested a way for residents to play their music on an outdoor speaker system around the pool/pool deck. Here original request was for an "iPod Dock" for residents to use on their own, but between the weather exposure and relative fragility of the iPod dock connector, I don't think that's the answer.

Any ideas/experience with such a "public use" audio system utilizing Apple/Android-based devices?

The Roqbot App seems like a good approach--Any experience with this or other similar systems?

Huge red flag!

It is NEVER a good idea to do what the property manager is wanting. Just think for a second what kind of music someone 'might' play over the system. Let me tell you, some of the latest music that can be found, really truly is not music and more 'artist expression'. Many times vulgar artist expression.
If the manager starts to say "No, there's no one like th...." cut him off. There is ALWAYS someone (or a few) like that around. Even if it's a retirement community, bored teen grandkids visting, etc...

To answer your question: 
A Bluetooth or Airplay device added to the system would allow anyone to push music to the system with an iPad, Android tablet, smart phone, etc...
But! On all these devices I've seen, it's a free for all. No login or authentication means anyone can take control of the system. Again, you have that person taking control of the system with his device and not letting anyone else on.

Again, this is just a very, very, bad idea. You need to explain to this property manager why.

I agree with the "Red Flag" reaction...But, she seems pretty set on the premise.

The more I look into the Roqbot service, the more that seems like the perfect answer to this request. Anyone deploy this?

Since you didn't supply a link in the 1st post, I didn't even look at it. After this post, I did a quick search and found it.

That actually looks pretty cool.
The only thing I have to question is the 50 free plays per week, then paying for each selection after that. The only info I found on the internet about how much credits cost to play a song is any where from $.50 to $2.50.
I also found where someone can pay extra to jump ahead in the queue. That doesn't seem fair or right. But probably wouldn't come up that often.
Also see they ONLY sell the service to business. I wonder if they would even allow what you are trying to do. Probably need to call or email them with a bunch of questions.