The ability to record yourself talking to someone/something, and later you can play it back. But instead of a normal recorder or your parents, it is… Emo.
A function that you can just tell Emo about your day and record yourself. Like having a diary, but electronic. And whenever you want to you can ask Emo to play the recording of a specific day. Maybe not as handy when you have to share an Emo tho (Thus more reason to get two 
). Perhaps you could also upload it to f.e. your Google account. If I’m not mistaken all data Emo gets is cloud-based, so when one Emo breaks and you need to get a new one, you can still access your “diary”.
The idea is to be able to hear yourself from the past, and not that Emo writes down everything you said to it. So I guess it’s only job will be to note the date, time and record sound. And maybe to some times ask its owner if he/she wants to make a diary recording, around times during the day that you usually don’t have anything to do (using AI it could learn at what times). That would make it a little more safe concerning privacy (not much, but at least a little).
Here is an example scenario:
To start your recording session you say:
“Emo, start/open diary.”
Immediately Emo notes the date and starts a recording of the day. When it’s ready it’s says something like “Ready” (or something else, in case DDL wants to copyright the word “ready”).
When done telling Emo about your day you give him a pet on it’s head (or some other gesture) and Emo will stop recording.
Whenever you decide to open your diary more times a day the recording will just become part of the same day (and in case you have to ask: starting a recording at 23:59 and finishing five minutes later on the next day will still count as the previous day).
To get memories from a certain day you say something like: “Emo, play diary september 20nd 2022.” Afterwards Emo replays the diary of that day.
Or whenever you are bored you could say “Emo, play me a diary.”
After hearing that it selects a random diary of any date, chosen by itself. And plays it. So you can be reminded from random moments/days you saved in the past. Over time you make your own library of your history. A next-gen diary.