What happens if the caregiver (me) has an accident and can't get to the phone, and neither can the patient?

We went with Medical Guardian. They didn’t try to pressure us in to getting extras we didn’t need and they were reasonably priced. My wife had the alert button on a lanyard she wore all the time. She, fortunately, never had to use it.

As others said: life alert around the neck.

Also iphone with Siri, with you at all times: you yell at Siri to call X.

"I've fallen, and I can't get up"

Life alert system

If outside you yell. You keep yelling until a neighbour hears you. Or you scoot along the ground until finding something to make a noise with, like a stick & whack something noisy to gain attention.

If inside & can't get up, you scoot along until you can reach a chair to either use to pull yourself up or pull things down to. Pull a corded phone down to you. Or find objects to throw at a mobile/cell phone to knock it down to your level.

These are from lived experiences elderly fallers have told me.

If you have a portable phone, you can ensure you alwears have it on you. Eg Wear an apron with your phone in the pocket when outside.

If a longer time frame (than a short recovery) is expected, a falls alarm pendant (or bracelet) are very useful & reliable. Some are user activated (so no good if you hit your head or pass out) but others are motion detected. I believe types differ, as may annual fees.

Not sure of your Husband's issues - would he yell for help? (My Mother has speaking issues now: a soft frail voice & cannot).

I got my mom a Lively medical alert 'necklace' to wear on the very few occasions when she is alone. She had it when she was mobile and it worked great when she had a fall & I was at work.
There are quite a few different devices out there that can alert emergency personnel if required.

There are devices that you can press a button and it will alert the company to dispatch EMS.
I recently saw a commercial for an Apple Watch and if there is a fall and no response it will summon EMS with the GPS location.
Does he have a phone that he can use? You do not even have to dial a number on a Cell phone for an Emergency Call most will show a bar or icon for an emergency call.
You do not even need to have an active account to use a Cell phone for an emergency call, as long as the phone is charged an emergency call is possible.