Considering spawners are crystal/gem like, being able to use a gem singer to locate them would be pretty neat for underground exploration. Personally i find it a bit too difficult to find tar beast spawners and such underground, especially when not using a minimap. Being able to use a gem singer to find them would be extremely useful.

While being able to find spawners is a good idea, I can see it being annoying aswell.
The main big difference between spawners and gems/life crystals, is that you don't always want to mine your spawner.
This could lead to the Gem Singer tracking spawners you already found when you don't want them to.