This is just a timer I've made the last 2 days. Belive it or not, It's the first time I use a output/Input and the first time I trigger something to complex entities. I'm impressed on how easy to use is the input system.
Timer have an activation entity, it's the left func_button, but you can change it to whatever you want. Middle func_button stops the timer, it's a little bit buggy when you stop it and then you activate it to continue timming. The right func_button resets the timer to 00:00.
I've put the original timer system behind the spawn. I'm giving the .vmf too.