I considered doing this - take screenshots of your screen constantly, OCR them and index them. It's fairly simple. However, there are some problems
- OCR constantly running in the background is power consuming
- What granularity do you take your screenshots? Imagine each screenshot is 500 Kb and you take one each second. This'd result in 40 gigs of data per day. How are we gonna store it? How many days data do you want to keep?
Since parent is taking power consumption and disk storage into consideration, it's fair to assume they are considering a local approach, meaning privacy is as good/bad as any other local data you have on disk today.
- OCR constantly running in the background is power consuming - What granularity do you take your screenshots? Imagine each screenshot is 500 Kb and you take one each second. This'd result in 40 gigs of data per day. How are we gonna store it? How many days data do you want to keep?