Website & terminal integration that reads last ~30 lines of stdout&stderr and suggests a solution/elaboration with links back to stackoverflow/forum post that it came from. Launch as open source and sell to enterprises that want to incorporate internal knowledge bases (extract Q & A from chat logs is huge) without leaking data outside the company.
Program that takes an AST and valid transformations, learn what kinds of ASTs humans prefer and offer a high quality auto restructure code tool that guarantees no side effects.
Company that I can pay a small subscription to that works to protect my attention, ad blocking has been done fairly well for free, but that is far from the only attention hog. Most app's notifications are just distractions and should be batched, only to be looked at at the end of the day. Should be easy to take a picture of paper spam mail and have the company get it to stop. Stuff like that.
Company that picks up anything from junk to valuables and either charges or pays you based off of the value of the stuff. As a customer I'd like to take a picture of the items, receive an estimate of cost or price and only have to interact with the company, no coordinating with craigslist rando.
IoT company that produces cheap place-and-forget devices that monitor long term potential problems in houses (major changes in how vibrations carry through the walls, moisture in basement)
EDIT more:
A purely audio interface to email, specific goal being usable while walking/driving to work.
Text preprocesser that estimates what you already know (tracks what articles you read, how much of them you read) and greys out/deempahsises stuff you likely already know. Having an estimate of what someone already knows could be huge for manipulating the forgetting curve & estimating the likeliehood of understanding what is in a piece of text.
Reddit/HN like site that ranks based off of amount of work done on the item, try to be more popular than bitcointalk. Plenty of ads targeting crypto holders.