DU Phone Cooler&Cooler Master is a free app from DU Apps. It speeds up your phone and improves its lifespan by giving you the ability to prevent your phone from heating up. It does this through a variety of functions, some automatic and some manual, that let you reduce CPU usage, nip problem apps in the bud, and see your phone's actual heat up to the second. It has a few other frills too, like monitoring charge time.
Just a few cool features
As soon as you open the app, you'll notice its two biggest features: real-time temperature monitoring and one-tap cool down.
The former is mostly useful to tell you how hot your phone is getting, versus how hot it is now. If you're wearing gloves and aren't bothered by the heat, but want to avoid the long-term damage that can come with a hot phone, you can see whether the temperature is stable or increasing by looking at this app.
The latter, though, does everything the app can do with one tap. There are other features, and you can use many components of the one-tap cool down manually. But with a single tap, this feature figures out what's causing your heat problems, and solves them (usually, in any case!).
A good analysis
DU Phone Cooler&Cooler Master is notable for providing an app-by-app analysis of what apps are using too much power and, hence, generating too much heat. It's this analysis that it uses to determine what apps to quit and which can remain open when you use its one-tap cool down, and it provides this information to the user directly through the app as well. Thus, a good deal of keeping your phone cool using this app is understanding which other apps are causing the problem in the first place. This is the area where DU Phone Cooler&Cooler Master helps the most.
A bit more questionable is the analysis it provides of the phone's temperature itself. Numerically, it's not often off base, although in our testing it reported cooler temperatures than were actually felt with older phones. Less consistent overall is the notifications it sends: it may alert you that your phone is too hot, only to inform you that it's at a normal temperature when you actually open the app.
This is just an annoyance, since if your phone actually is hot you can still use the app's one-tap cool down, and after updating the app, occurrences of this went down (although they weren't eliminated entirely).
Quality, though not perfect consistency
Ultimately, DU Phone Cooler&Cooler Master wraps up the most important phone cooling functions into an easy-to-use package. It's simpler than many other cooling apps, and when it works, it works well. Although our testing indicated that it wasn't perfectly consistent, the app is updated often enough that it's still worth trying on your phone.
Just keep in mind that if you want to cool off your phone, simply running a cooling app can only do so much: some problem apps might have to take a break now and then.