Busy execs don’t have time for the interruptions created by the spam calls that are increasingly targeted at their smartphones. But there may be at app for that.

Now that smartphones are the tech tool du jour for both business and personal use, telemarketing spammers have begun to prey on their owners in much the way they did landlines only a few years ago.

That doesn’t mean you have to burn precious cell phone minutes answering their calls or reading their texts.

As the Apple commercial likes to remind us: There’s an app for that.

The two most popular smartphones by far — the BlackBerry and the iPhone — both have software that will attempt to block most of the known spammers operating these days.

For the BlackBerry, you can get Call Control Pro from the folks at EveryCall. There’s a free version that blocks the top 100 spammers; the upgrade ($7.99) gets you protection from the company’s entire database of spammers.

Over at the iPhone’s App Store, there’s software called “Call Block” that’s only $1.99 (there’s no free version) and the software gets pretty lousy reviews from buyers. But for $1.99, it could be worth a try.

The trouble with all of this software is that it relies on known spammers. Any app of this sort would necessarily need almost constant updating as spammers change numbers  almost hourly.

Most of us rely heavily on the caller ID built that’s part of all phones to screen unwanted or anonymous calls. Letting unrecognized numbers to go to voicemail is one answer; few spammers leave a message. But it’s also a surefire way of missing some important phone calls just because the number’s unfamiliar.

You can also register you mobile number with the National Do Not Call Registry. It takes just a few minutes, is totally free and only requires that you provide a confirming e-mail address.

Once you register your number, the registry sends you a confirming e-mail that you have to respond to in order to complete the process. Then telemarketers get 31 days to purge your number from their lists.

Of course, signing up with the registry won’t block spam from the folks who bank with or have a credit card from.

Anyone out there with better suggestions for keeping spam off your mobile phone?