Describing iStat (an app for iPhone/iPod touch) is like blind men describing an elephant. One might say it's an iPhone app that magically frees up system memory. Another might say it shows you what's happening "under the hood" of your iPhone/iPod touch. A third describe it as a remote monitoring app for Mac, Linux, or Solaris machines. And a fourth might say it's a pair of useful network tools, namely ping and traceroute. Well it's all of those things and more.

Note: Even if you didn't understand much (if any) of the above, don't tune out just yet. You may still need iStat, if only for its "FREE MEMORY" button, which can avoid app crashes and freezes, and allow you to use certain memory-hungry apps without restarting your iPhone/iPod touch first. 

Let's start with that feature since it's the one anyone and everyone can benefit from. If you have any apps that came with instructions like, "for best results restart your iPhone/iPod touch before launching this app," iStat's free memory button may be just the ticket. Suffice it to say that your device has a limited amount of system memory (not the 8, 16, or 32GB of storage) that is used for iPhone/iPod functions as well as for running apps. Needless to say, some apps require more free system memory than others. Moving right along, system memory is allocated to apps when you launch them but not all of the allocated memory is released when you quit the app. And so, the amount of system memory available for apps decreases over time. 

One way to release all of the unused but currently unavailable system memory is to turn your device off, then back on (i.e. restart it). When it comes back up it will have as much free system memory as it's ever going to have. So some particularly memory-hungry apps (including many games) run better if they are the first app you launch after restarting. 

iStat's FREE MEMORY button does the same thing as restarting with regard to system memory. This pair of images shows what happens when I press the FREE MEMORY button on my iPhone 3GS: 

The top image shows the memory situation before I tapped FREE MEMORY; the bottom image shows the result. As you can clearly see, iStat increased the amount of free memory I had available from 45MB to 140MB. Had I restarted my iPhone instead of using iStat's FREE MEMORY button, the result would have been about the same. The difference is that tapping iStat's FREE MEMORY button it took about 10 seconds to free up 95MB of system memory, while restarting took a little over one minute.    

I'd pay $3 for that feature alone, but wait, there's more... In addition to freeing system memory and providing  information about how that memory is being used, iStat also monitors other iPhone/iPod touch functions as shown below:

And, it can email your iPhone/iPod touch's UDID (unique device identifier) and MAC (Media Access Control) address. If you don't know what those things are, don't worry. Some people never need them. But if you ever do need them, you can not only look them up in iStat, but you can also email one or both to yourself or whomever needs them. 

And that's not all... iStat can also remotely monitor CPU, memory, disks, uptime, load averages and more on any Mac, Linux, or Solaris computer. So you can keep tabs on your machine's health right from your iPhone. Just download the free iStat Server for Mac OS X, Linux, or Solaris from http://bjango.com/apps/istat/ and run it on the target machine. Here's what that looks like: 

When I'm at home, I see the server running on my MacBook Pro automatically via Bonjour. To use it when I'm not here I'd have to either set up port forwarding or have a static IP address, or both. I haven't done that because my ISP doesn't offer static IPs but it looks relatively easy if you do have one. 

iStat also contains two other tools -- ping and traceroute -- both of which can help you troubleshoot network issues from your iPhone. Here's what they look like: 

The only thing I might complain about is the static IP address for remote monitoring (and I'm not even sure iStat is to blame).  

And that, my friends, is iStat in a nutshell.

The Bottom Line

I would gladly pay $2.99 for iStat's FREE MEMORY button alone. So the other (somewhat geeky) features are just icing on the cake. Even though I don't use those features much, I'm glad to have them just in case.    

Note: iStat is currently on sale for $1.99 (regularly $2.99).