Hearthpwn

As I find less and less time to play hearthstone, I keep thinking a decktracking app would boost the experience for me (since I'm not paying as close attention lately). What is a good option?

IMO the HS Decktracker from hsreplay.net is the best one. Very easy to keep track of everything, as well as adjusting what you want to see as an overlay while you're playing. The Android app works fine as well and their website also allows you to check a lot based on the data they collected from everyone that uses their tracker. I know it has definitely improved my gameplay and the way I look at my decks. 

For me it's hsreplay's Deck Tracker

https://hsreplay.net/downloads/?hl=en

for a better experience go to settings and unmark all modes except Ranked, that way the tracker will only count your ranked match ups.