Get Two Android Apps That Display Crucial Phone Information for Free

Kannon Yamada 01-08-2013

Sometimes I need to check information on my phone that the notifications bar doesn’t show – such as GPS signal strength and CPU temperature. For example, when traveling, knowing whether your mobile is on the verge of an overheated shutdown or if your GPS signal might soon conk out, helps a lot. I spent a lot of time puttering around with different ways of visualizing this data and discovered two apps that stand out: Power Line and Cool Tool.


Power Line and Cool Tool allow you to monitor a huge amount of information, regardless of what you’re doing on the phone. They use a feature of the Android operating system called “screen overlay” which allows apps to display images over other apps. While sounding similar to the Android notifications bar, which displays at the top of the screen, screen overlay appears anywhere you want on the screen.

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Power Line

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Power Line shows all its information without text – using extremely minimal lines. Although Power Line can display fewer kinds of readouts than Cool Tool, its colorful bars look extremely good and are much easier to setup. To get started with Power Line, you only need to fire the app up. If you need to add additional lines, navigate to “settings” and hit the “+” button in the upper right corner.power_line_start

Core Features

  • The Power Line app displays your phone’s information using customizable, colorized bars, which it lays out in one of three positions: (1) Top of the screen; (2) bottom of the screen; (3) center of the screen. You can alter the color, thickness, positioning and transparency of these bars.
  • Large number of readouts: Power Line provides thirteen different readouts – there’s a fourteenth option to include bars as decoration.
  • Full screen bars/lines: The colored bars can span the entire length of the screen. For example, using the mobile signal bar readout, when in an area with great cellular reception, the bar spans the length of the screen. The colors of the lines can also change, depending on their strength — for example, if a cellular signal is strong, the color can be set to turn blue.

The Good

  • Minimal aesthetics: Power Line features extremely minimal graphics – it’s just a bar.
  • Inexpensive: The paid version of Power Line costs $1.49.
  • Beautiful: While Cool Tool focuses on raw functionality, Power Line emphasizes appearance. Below, I enabled several bars against a black background, for contrast. You can see that the lines are of varying thickness, color and positioning.


The Bad

  • Free version heavily limited: The Free versions unfortunately doesn’t come with very much, aside from the battery and signal strength indicators. If that’s good enough for you, though, you won’t need to purchase the paid version.
  • The clock available in Power Line, predictably, is a line. To me this made it extremely difficult to gauge the time – looking at the sun provided a more reliable estimate of time.
  • Difficult to distinguish between each line: You can only tell the difference from each line by changing color, width, transparency and positioning. Oftentimes, even with different colored lines, I found myself not really being able to tell whether my battery was overheating or if it was simply low on charge.

Cool Tool



Out of the two apps, Cool Tool possesses the most functionality, with less emphasis on aesthetics. It features a huge number of readout options, including GPS signal, cellular network signal strength, free RAM, battery temperature and more. One of the more interesting features of Cool Tool is that it can function as a task killer – though I don’t recommend using this feature on any Android versions newer than 2.2, Froyo. Additionally, it has several custom themes that you can download for free.

Core Features

  • GPS information: Cool Tool includes GPS monitoring. Below, you can see the GPS signal strength in purple. Typically any rating above zero indicates a functional connection. You can also choose to set the GPS to display as a graph, which can indicate whether or not GPS signal will soon drop off.
  • Adjustable positioning: The Cool Tools display can appear anywhere on your mobile. To change its position, simply use the virtual joystick to move the display around.


  • Text, histogram or graph display: Cool Tool can display information in either text form (such as showing battery temperature in degrees Fahrenheit), as histograms or graphs.

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The Good

  • Themes: Cool Tool also offers a variety of free themes. Some increase the size of the graphs and readouts. Others change the color. Cool Tool gives a great deal of leeway to those with custom icons and launchers.
  • Highly customizable: There are hundreds of customizable sensor display options in Cool Tool.
  • Ridiculously feature rich: It can monitor almost any metric available on your phone.
  • Broad compatibility: Cool Tool works on almost any phone. Believe it or not, it worked on all of my many Android devices, going back as far as Android 2.1, which is paleolithic-old in Internet time.

The Bad

  • The free version includes an ad, but this only displays during the setup process. Overall, this isn’t much of a negative.
  • Turning on too many gauges will drain your battery faster.
  • Complex: It can take some time to properly configure the app, as there are hundreds of configuration options.


Comparing Cool Tool to Power Line for me is very difficult; over the past few months I’ve alternated use between the two. Are they worth purchasing? Yes, although Cool Tool’s Pro version only exists in the Amazon app store and Power Line doesn’t include ads. It comes down to this: If you prefer raw minimalism, go with Power Line. If you want a more feature rich application, give Cool Tool a try.

For those of you looking for all kinds of hardware info on your phone, check out Erez’s breakdown of Elixer 2 Elixir 2 - A Free & Insanely Powerful System Information App [Android 2.1+] When I first wrote about Elixir, that post made quite a splash. It turns out many people want a good, free, system information tool for Android. Well, for all of you out there, I have... Read More . I can personally vouch for Elixer 2’s thoroughness. It will tell you all kinds of things about your phone.


Does anyone else use overlay tools? Let us know in the comments.

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