I'd second the Apple Airport Express. It's likely to be a little more expensive then the others, but it's also probably going to be useful to you around the house as well.

Beyond AirTunes, it can be used as a wireless range extender, printer sharing, or even as an ethernet to wireless bridge for connecting a non wireless computer to your network. I've found mine well worth the investment, especially when paired with speakers that can draw power over USB. This has allowed me to just plug in the Airport express somewhere, and have music anywhere within range of my network. And the convenient thing is that it allows for several profiles to be stored on it, so you can easily switch between all these configurations without having to set everything up again.

The current (and older express units) all support WPA2, so encryption shouldn't be a problem.