Re: other services.
I'd like to implement something akin to Google Photos but where all your images are encrypted before going up to the cloud for storage. All the fun face recognition features and indexing would have to happen on your phone, but phones are plenty powerful enough these days to do that while you're sleeping and your phone is plugged in and charging.
I'd like to implement a simplified personal assistant like Google Now, that doesn't depend on sending your personal data into the cloud. Again, phones are so powerful and they already know so much about you based on local context, that I think there's a big opportunity for making a "good enough" assistant that doesn't compromise your privacy.
More mundane, but I think still very useful, is being able to store your contacts in the cloud, but making sure they're encrypted with a local key you control, so the storage provider (e.g. Zood) can't see your contact list.
An actually trusthworthy VPN provider. Mozilla entered this space a couple months ago, and I think it's great that there is at least one trusthworthy VPN brand now. It's a very confusing market for people to navigate, but I'd like to earn the trust of people so a Zood VPN product would become a viable service.
Along the theme of helping people extricate themselves from the advertising and surveillance economy, a service that helps people remove themselves from these junk snail mail lists. You can do it on your own right now, but it can be overwhelming.
I have lots of other little ideas, but they aren't quite ready for discussing. :-)