If you get stuck inside and want human interaction, a little video chat is a long way. While most laptops come with built-in webcams, desktops don't, and laptop cameras can break at any time.
Unfortunately, USB webcams are currently difficult to obtain due to the increasing demand for video conferencing. With a little free software, you can turn your phone - or any replacement smartphone - into a webcam for your PC.
For Android phones: DroidCam
If your phone is running Android, you can use a free app called DroidCam to turn it into a webcam. The free version offers everything you need to get started. However, a $ 5 upgrade to DroidCamX offers 720p video and an experimental option with a high frame rate and small advertising banners. If you plan to use it frequently, it's a worthy upgrade, but I found that the experience with the free version was pretty solid.
To get started, you need two software components: the DroidCam Android app from the Play Store and the Windows client from Dev47Apps. After installation, make sure your computer and phone are on the same Wi-Fi network. An IP address should be listed in the DroidCam Android app (e.g. 192.168.1.91), which you can enter in the desktop app to connect the two.
Be sure to select the Audio check box on tablets for students if you don't have a microphone on your PC. Click the Start button and you should be connected. Most video chat apps should recognize DroidCam as a valid webcam. However, you may need to restart them if they ran when DroidCam was installed. (Skype is an exception that can be a bit difficult. You may need to use the old version, which is not from Microsoft Store.)
In my experience, DroidCam worked well enough. Friends on the other end said the SD video quality looked good, but there could be some lag in the video. Some had problems with the audio from my phone, so my computer's microphone was still ideal.
You can make some settings, e.g. For example, the camera to use (front or back), the microphone to use (camera or speakerphone), and some battery saver features, but you only know that this is probably not the case as well as a traditional webcam.
If you'd rather connect via USB than Wi-Fi, DroidCam can do that too, although some advanced finagling features with some phone-specific drivers are required. For more information, see the DroidCam instructions here. Even if you stick to Wi-Fi, you may want to charge your phone while video chatting as this will drain the battery quite quickly.
For iPhone users: EpocCam
If you have an iPhone, EpocCam is the app I would recommend to turn it into a webcam. It is actually cross-platform and available for iPhone, Android, Windows and MacOS. However, in my experience, DroidCam is the superior option if you have a choice. The EpocCam ads are very intrusive and contain only a few functions in the free version, so that a paid upgrade is almost necessary. DroidCam offers better video and audio overall, but your mileage may vary.
To use EpocCam, download the EpocCam app on your iPhone and download the drivers for Windows or macOS. You may need to restart your computer after installing the desktop software.
After the restart, you can start the EpocCam Viewer app on your computer next to the EpocCam app on your phone to check if it works. As long as the two devices are on the same Wi-Fi network, they should connect without additional steps. EpocCam should appear as a webcam for zoom, hangouts, or other video chat applications you use.
The free version of EpocCam is quite limited as only the rear view camera is available (unless you rate the app in the store). The free app also has some pretty annoying full screen ads and a watermark on your video, but in my tests it worked as well as expected. You probably want the paid version if you want to use it more than once or twice.