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Well, your going to be doing a fair amount of programming to accomplish this... I don't mean to "harsh your mellow" but a lot less sophisticated method might work better... How about a watch with an alarm?.... That's what my dad uses....

It would be easy enough to have the robot say something at a specific time of the day. It would be easy enough for the robot to know if it has already said what it needs to say for that day. The facial recognition is easy enough. Where the problem comes in is that you want the robot to roam the house looking for your dad. That requires some advanced nav programming. There is an app called Roborealm that allows for pretty easy nav, but you would have to tie the two apps together. There is a bridge built to pass variables from ARC to and from Roborealm already. I own a copy of roborealm but havent had time to play with it much at all.

Anyway, as richard said, an alarm on a watch or in the house would be far cheaper, probably more reliable and far easier, but if your up for the fun, there are ways to do it.