The best ideas really are the simplest (and most obvious sometimes) ones. This app, NumberKey, is a case in point.

17-inch notebooks are big and bulky to carry around, but sometimes I miss the numberpad, like when I’m dropping in a credit card number or doing an Excel spreadsheet, and using two hands to pound digits is just annoying next to the numpad’s one-handed efficiency.

Enter Numberkey, an iPhone app that turns it into an wireless numberpad for your Mac using Wi-Fi. The setup is quick and simple, and it works like a charm, apparently. There’s a small desktop client that goes with it, and it’s all only $1.99 and is available for download right now in the App Store.

And it even comes with four skins to cover every style of modern Mac keyboards to match up well with any look you desire. Heavy spreadsheet or financial people should be overjoyed.