If you have an old Android phone that you no longer use, you can easily use that phone as a webcam using free apps such as IP webcam. However, if there’s no WiFi available, you can use the Smartcam app as it even works over a Bluetooth connection.
You can set up a connection over Bluetooth or WiFi. The app also lets you choose the video resolution with the support for full HD if your device is capable of it. Other settings include the option to hide camera preview on the display to conserve battery and to keep the screen from going into sleep mode.
One advantage of Smartcam is that it can even be used with video chat software such as Skype and Google Hangouts. That said, in order to use the app, the Smartcam software has to be installed on your computer. Currently it only supports Windows and Linux machines.
The connection quality over WiFi is top-notch with a lag of just 1 second, while on Bluetooth the lag varies between 2-5 seconds.