There are many apps that allow you to use your smartphone as a webcam. In this video, I highlight the app DroidCam for Android devices. DroidCam allows for wifi (internet or bluetooth) or wired (via microUSB) connection. The app is free, simple to use, and serves as a very solid stopgap for those in need of a webcam.
DroidCam app: https://play.google.com/store/apps/details?id=com.dev47apps.droidcam&hl=en
DroidCam PC program: http://www.dev47apps.com/