I use Simple Notepad[0] on my android phone. It has a checklist option that I go to the store with, which works much better than the list I write, which works much better than the list I keep in my head.

[0]https://play.google.com/store/apps/details?id=org.mightyfrog...

Been there and tried it - went back to paper.

A piece of paper is 'always on', it wraps around the push bar of the food cart so I don't have to make adjustments to hold the 'device' and steer at the same time, or keep fishing the phone out of my pocket and unlocking it, nor from the cart itself, while ensuring I don't drop any shopping on the screen or stray too far from the cart and give someone the opportunity to grab the phone.

The only way I'd go back to using a smartphone is if the cart had a lockable universal smartphone cradle. Bonus points would be given for a built-in charger - provided the stores maintained everything so you didn't need to 'test' the carts outside to find one with a working charger and cradle.

Adding items to a shopping list is actually one of the relatively few things I end up using my Amazon Echo for. It's easier to add and I don't forget my phone when I go to the store (or end up going when I didn't plan to). I'm not a huge Echo fan overall but I do find it good for that.