My mum was offered a mechanised 'dosset' box that was to be filled by the local pharmacy and gave off a sound when tablets were due and the tablet compartment remained accessible for 30 minutes then closed and would remain closed till it moved on to the next dose.
I think it could give multiple reminders in the 30 minute time frame while the tablets were available in case the PWD was out of the room etc when it went off the first time.
It was offered after a SS assessment and free of charge, 2 of these would have been given so the pharmacy always had one ready to replace an empty one.( pharmacy deliver weekly)
It wasn't suitable for mum due to hearing problems but might be a solution for you. As others have said, next option is carers to prompt, this is what happened with mum, she didn't trust me and so external help was needed.
It only took a day or so for SS to arrange it, mainly as at the time mum hadn't had a financial assessment and so SS were picking up the tab for carers to come in, essentially for a few minutes for prompt meds and complete paperwork 3 times a day, it must have cost a fortune but l refused to get involved at that stage (now thankfully passed) as anything l did was wrong or looked on suspiciously as she felt l was trying to make her crazy to get my hands on her money/house etc