SteemWatch lets you set custom notifications with heaps of different filters so you get alerts when things happen.
It arrives via a steemit.chat message like this one I just got a few moments ago :
I just had the sudden urge to make sure more people are aware ..
Check it out at steemwatch.com
In other news, we're in the final hours of the YOURBTCC exchange poll and are in an extremely close second place :