The scenario I would want to have this is if I want to quickly drain the battery so I can charge it fully again. Some say that this will help extend the battery life by fully draining/charging the battery.
How to drain the battery quickly?
Android Enthusiasts Stack Exchange is a question and answer site for enthusiasts and power users of the Android operating system. It only takes a minute to sign up.Sign up to join this community
This question is along these same lines: What causes battery to drain faster than it can charge?
So there may or may not be an app designed to drain the battery but you probably just need to turn on an app that uses the GPS. This will help to fully drain your battery but I don't know that doing so before recharging will extend the battery life.
Do not do this. You are actually harming the lifespan of your battery when fully discharging it before a recharge. See this site for a discussion of how depth of discharge affects battery life.
The only reason you might want to fully discharge before a recharge is if you have a NiCad battery that is susceptible to the memory effect. Your smartphone most likely uses a Lithium-ion polymer battery, so there is no good reason for you to totally discharge your battery. The lifetime is longer if you have a shallow depth of discharge.
I know that my phone -- HTC's Evo -- actually has a diagnostic tool thats sole purpose is to drain the battery as fast as possible. Open up your dialer and enter:
You don't need to press send or anything. A recent update for the Evo blocked these tools so hopefully you can still access them. You can also look up device specific codes if yours happens to be different. Rooted users have found a way to get these tools back.
The utility turns up brightness all the way, prevents sleep, turns on the camera and flash, turns on the GPS and constantly polls it, etc. Basically everything that can drain the battery but not damage the phone is done (ie it doesn't constantly vibrate because that would probably be bad).
Just play The Elements. A very CPU-intensive game. If you add a lot of stuff to make the simulation very slow, you are sure to use the CPU in full.
Meanwhile, you could use a GPS fix to constantly use your GPS. And you could leave your Bluetooth on. All this at the same time (especially with the Samsung Galaxy S2 & Cyanogenmod) you might end up using more power than your phone can recharge.
I found a combination that draws more than 2 Ampere on my phone without requiring any non-built-in app.
Brightness to the maximum. Obvious yet easily forgotten.
Disable adaptive brightness. Sleep after 30 minutes, or better: play a video.
Picture-in-picture video streaming (YouTube, Netflix,...). This keeps active:
A fan to avoid thermal throttling
Some apps show the total battery drain.