This Primos® Bombshell Push-Style Hen Turkey Call works great for people with no finger movement. I have no dexterity in my fingers and I can work this call with no problems. I attach the call with the velcro strap that comes with the call to my crossbow mount. Then I hook my fingers into the string that is attached on the other end of the turkey call and give it a tug to make sound. There are many different ways to attach this to your shotgun or crossbow. There are also a wide range of calls you can produce depending on how you pull or push on the call. It produces realistic yelps, cutts and purrs. Below is a picture of it mounted to my crossbow mount and a video showing how the call works.
Not a very good picture but you can see it is attached to my crossbow mount.