Hi astroman,
In addition to what Garzie said, there are also electric/battery powered - plant spray bottles that have an on/off switch so you don't have to keep pressing the button.
You could:
- Place it on a table
- Press the on button
- Turn around and have it spray your back for you
Here's an example, notice the "on" button (it stays on after pressing it once):
https://www.amazon.com/pioneerworks-indicator-adjustable-gardening-fertilizing/dp/b0b3j4t5m8