Android: IP Webcam turns your Android Phone into a network camera by streaming the phone's camera over its Wi-Fi connection for remote viewing.
Install the app, tweak the settings (login/pass, resolution, image quality), and then simply load up the URL it gives you in a web browser (I used Chrome for testing) or a client that accepts streaming video (I used VLC).
Below is the setup I used to stream a view from my dwarf Cichlid tank to my desktop. I used two suction cups and a black hair tie to secure the phone against the glass. The same setup could be used to peek out your window at your parked car or out your front door.
Although the individual stills are blurry, the overall video itself was decent enough quality. While it won't replace a dedicated HD web cam or security camera it does add solid remote-viewing capabilities to your Android phone and requires minimal setup. IP Webcam is free, you can download it by searching for "IP Webcam" in the Android Marketplace or by scanning the QR code at right. For an alternative Android application check out previously reviewed Qik. iPhone users will want to check out iWebCamera for similar phone-to-desktop streaming.