So....here was my reply.
I've always wanted to do this, but haven't - lack of time, I guess (isn't that always the excuse these days!) Anyway, I was thinking of having a "Big Ear" contest. I have a chart on my website for this. A student would mark an ear for every hour they listened. There could be some sort of time requirement (1 month - or something like that) and everyone who finished the chart in that period of time would be the winners. You could have some sort of award for the winners. One award I've thought of for some of my students who accomplish big tasks are the earbuds I have on my site. They are cute and perhaps it's not something they have. It would encourage more listening. Here is the link to the page with the Big Ear chart.
Hope this helps!