Customize Ringtone Based on Tracking Number/Call Setting

We got a great question/request from a client who is looking for the ability to customize a ringtone that the agent hears based on either a tracking number or call setting. Any additional flexibility on this (other than customize based on user) would be awesome!

I could see this being valuable for companies who have multiple businesses (as our client does) but also for other things like designating a certain tracking number as higher priority so the differentiated ringtone could help signal to the agent the urgency of picking it up, etc.