You could use your smartphone for recording videos for webcam exercises. There is also the possibility of recording video for webcam exercises using your computer's webcam.
There are some drawbacks:
- image quality of your smartphone or webcam recording may be inferior. When using your webcam to record video, the quality of your internet connection plays a part in the image quality of your video.
- image stability may be bad when you or someone else holds the smartphone in their hands when recording.
The situation you are filming in has consequences for the sound quality of your recordings. When you are filming in a situation with background noise, use a directional microphone mounted onto the digital camera (or headphones with an integrated microphone when recording on a smartphone, or a microphone connected to your computer when recording using a webcam).
If that's not enough, you could consider wiring the actors with microphones, which send the sound to the camera or record the sound separately. This last options will require some editing on your part.