It may be all you need is this adapter, shown below..

Phone on Fence Shown with Wide Angle Lens

Adapter is shown to left by itself.  To the right, the adapter is shown mounted on the QM-1 "Quick Mount" Portable Camera Mount.  Phone is shown using a Wide Angle Lens (NOT INCLUDED), BUT this lens is available with the Smartphone Kit.

View from 18' setback, 10' high

View as seen using Smartphone, .45x lens and QM-1 Camera Mount.  Unedited except for captions.  Note:  Newer iPhones (11 and up) and some other phones have a wide-angle lens built in.  To test, stand at the back of a tennis court and look at how the court is covered by your phone.  If you can see the near corners of the doubles alley, you are probably good with just the adapter.  Otherwise, consider the Smartphone Video Package or if you already have a QM-1, then the Smartphone Kit which includes the adapter and a high-quality wide-angle lens.

Your smartphone may be the best camera you have!  GoPros and other action cameras are great, but your phone may also be the most convenient and reliable piece of equipment you have.

Shipping is added in the cart at $4.00.

Smartphone FAQs

1.  How do I know if I need to buy a wide-angle lens?  If you have an iPhone 11 or newer, you already have a built-in wide-angle lens.  For other phones, stand at the back of the court and face the court, seeing how wide the viewing angle is. If you can see the corners or of the court (at the outside of the doubles alleys, you probably have a wide enough angle). If in doubt, you can always order the lens later.
2. How’s the battery life?  This varies by phone manufacturer and by age of phone. My Galaxy Note 9 will film for an hour and half and still have 66% battery left. According to SwingVision, who uses only later-model iPhones, you should have 80% battery life remaining for a two-hour match.
3. How much storage do I need? We recommend a minimum of 10 GB.
4. Will it overheat? On a warm day in the direct sun, there’s a very good chance it will overheat. Some kind of shade, maybe like this one, will help tremendously.