Look, you're going to have to deal with the TSA, baggage fees, and all sorts of other junk to hop a flight, so why not make paying for the ticket a little less painful at least? Hopper might be able to help. It came to iOS a few months ago, and now it's on Android. Just tell it when you're flying and to where, then Hopper figures out when you should buy.

Hopper uses large data sets of flight prices and historical trends to figure out when prices are going to be lowest. Hopper also lists current prices for flights in the app, and when it detects that prices have changed, you'll get a notification. Supposedly it helps you book flights in under 10 seconds too. Oh, and there's a rabbit wearing reading glasses in the app. That's a point in its favor.

Adding a new trip to Hopper is a snap, but you can't stipulate any parameters other than dates and location for price tracking. Hopper seems to mostly pay attention to the cheapest flights, which aren't always the most convenient. I would probably pay more for a flight that leaves at a reasonable hour and doesn't have a three hour layover, but that's just me.

Hopper - Watch & Book Flights
Hopper - Watch & Book Flights