I love that ADHD sometimes makes us forget whether or not we've taken our meds to control the ADHD! I recently found out that you can buy caps for your pill bottles that show you when you last opened the bottle! It's a life saver sometimes. Here's one from Amazon.
I have mild cognitive impairment so I'm not sure if this would help your mom or not. I think the product you are looking at might work. I actually use timers on my mobile phone to remind me to take my medication. The problem, though, if I am not able to take the medication for a few minutes after my timer goes off for whatever reason, and I did not hit "snooze", I have hard time remembering if I took the medication or not. My husband found these pill containers with a count-down of the time the bottle was last opened so using the alarm on my phone and these bottles help me keep everything straight. You can find these bottles here.