Long battery life has always been one of the hallmarks of BlackBerry devices, thanks to some clever architectural decisions by RIM: email is compressed, and the BlackBerry servers in the network handle the chattier parts of internet connections so the handset can turn the radio off more quickly to save power. But as third-party apps become more popular, not everything you install is as efficient as the built-in tools. BlackBerry is one of the few mobile operating systems with true multi-tasking, which means that the apps you run get to carry on running. Couple that with the way BlackBerry handsets have been getting sleeker — with less room for a hefty battery — and the legendary BlackBerry battery life can start to eke away.
To help you rein in some of the third-party apps that could be running your battery down, RIM has released a free Application Resource Monitor utility that can warn you about apps that are using too many resources or turn them off automatically.
If your BlackBerry comes with OS 7.1 pre-installed you might already have ARM installed (look under Options > Device); if you upgrade your handset to 7.1 yourself you can now get the utility from BlackBerry App World — once installed, it shows up on the list under Options > Device rather than as a separate app (if you can't find it in App World, check if you're running the right version of the BlackBerry OS).
ARM turns on automatically when you install it, but it's set to err on the side of caution by turning demanding apps off if they're using too much CPU time or waking up too often in the background rather than just warning you. If you leave streaming audio running the background or flip away from a game to answer an email, you might not want them getting turned off without warning — although if they do, it's a sign that the app isn't as well written as it could be. Games don't usually need to be repainting the screen in the background when you can't see it and RIM has guidance for app developers on how to avoid getting turned off by ARM.
You can switch to getting notifications about apps that might be draining resources instead of having them shut down automatically, and you can explicitly tell ARM to ignore streaming audio applications. You can also whitelist any apps you want to allow to use more resources: when you get the notification for an app (in the Notification View on the home screen along with all your other alerts), you can choose 'Do not monitor this'. If you change your mind later and decide that you'd rather have the extra battery life, you can take the app off the whitelist on the ARM screen (you can't add apps before ARM shows an alert about them).
There aren't any obvious settings to fine tune how sensitive ARM is, but if you type FLTR while the ARM dialogue is open you can choose how demanding an app can be before triggering it (RIM calls the 120 default intentionally conservative) and how quickly ARM starts monitoring after you turn on your BlackBerry.
Making the settings more sensitive will mean far more applications get detected by ARM. Leave it on the defaults and only apps that are really hammering the battery will show up.
As the processors and radios in smartphones get faster and more powerful and we run more apps that connect more often, the laws of physics mean that battery life is going to suffer unless you're very disciplined, or you have some help.
The difference that turning on ARM will make to battery life will depend on what apps you run and what impact they've been having on your battery life. If apps updating the screen or running the radio too much isn't what's using up your battery, then ARM won't improve it. But it's a nice compromise — it's not complicated to use, you get lots of information, only badly behaved apps will get turned off and you can whitelist demanding apps you like enough to give up battery life for. Plus you can give developers feedback and hopefully see more polite apps in the future.