If there's a rule of thumb when it comes to apps, it would probably be simpler is better. True to this adage is Toronto-based app Marco Polo, which is designed to help iPhone users locate their phone when it's mysteriously gone missing in one's general vicinity. This won't help if you left your phone at the bar, but it's perfect when it's become wedged in the couch and you're pulling your hair out trying to find it before leaving the house.

When you can't find you're phone, you merely call out "Marco" and the phone returns the call with "Polo." Nifty. Thankfully, you can also customize the call and response if you're not into this combination. That's it. That's what it does. Since being released, it's become the most downloaded paid utility app in over 80 countries. It'll cost you $1.19 for the service.

There are a few downsides worth noting. As wonderfully simple as the app is to use, you'll have to keep it running in the the background for it to work when you need it. That means that it shows a red line across the top of your screen pretty much at all times.

Depending on your degree of anal retentiveness, this will or won't be an issue. My phone also tends to randomly bark "Polo" at me when I haven't said "Marco," but I suppose a little bit of this is to be expected, and if you're prone to lose your phone might not be much of an issue.