well, none of these are really implemented (yet) but here you go

SW Only

1) An all-in-one transport app. You'd have a single credit wallet you could re-charge on a monthly/weekly/as-needed basis. You set in your profile for how long you are willing to wait for a ride(lets say +/- 15min), and how far are you willing to walk from your current location(lets say r500m) + other criteria if you please(like ferraries-only:). Rates could be something like few cents/km for "civilian" drivers(standard car-sharing - could be problematic depending on the legislature/generated profit for the driver), few bucks/km for cabs, pub transport based on routes/times and - dynamic pub transport routes per km as well. Lets say there is a after-work beer with colleagues planned so you can't drive to work by your self. During breakfast you just choose a destination(predefined for freq. places), desired time and a "hitchhiker sign". All drivers doing the same/similar route(with criteria compatible with yours) would be notified .. a few "accept" clicks away/maybe a quick look at the drivers profile(badges/km driven/reviews etc) and your off to work. No drivers available? Your app would show you all public transport possibilities(color coded based on compatibility with your criteria) + cabs in your area - few clicks away and you're set(either buying a ticket or ordering a cab). Double-validation for payments based on transport type - no more waiting on a bus stop for 2 hours watching 100's of driver-only empty cars going your direction + a public API would mean that bus companies could also use small 6-8 passenger buses and dynamically create new/amend existing routes based on the demand(200 people heading to a business park across town(C) from destination A, 100 from B to D(which is near C) between 0800 - 0900 > change route via B .. if time intervals are met(like 1h from A - C) ) ++ all the data flowing your direction could also be used as a waze alternative for even better routing +++ you could profit by selling api data/on % from commercial transport partners) + have awards for car-share folks like free oil/filter changes after 10k km/free coffee after 20km between 2200 - 0600 etc..). If you are in EU, these projects are highly welcomed..

2) We need a distributed decentralized(p2p), no-authority write once read many storage solution for "our civilizations data" like news/general knowledge. It has to support versioning, encryption, deduplication, store synapses between relevant data, be self-healing, layered, nodes monitoring/promoting(demoting)/caranteening each other if needed, role-based - build on premise that all* of the nodes are/can become malicious actors(..). Everyone should be able to run a node on his nas @home/mobile device, assign roles to his devices etc .. general storage for all things public.. + it should support anonymous document uploads(lets say an indenpended journalist from syria wants to get his/her story published / someone working in a big-co comes across some very interesting public-interest documents he;d like to publish and doesn't trust honey-pot assange/media) - all big problems on their own .. regardless of the client app using the data(if you are running a auto-moto/pro-(enter political party) website, you may apply as much filtering as you wish), the user should still be able to get/contribute to the "publicly-generated" synaptic nw of a news story as stored on the backend + this is the bare minimum for other systems we desperately need to reform(the "no-trust" premise of it) so a good way to dive into this problematic

3) services on top of 2) .. and there are many ..

4) DNS, routing, ssl/alternative, smtp replacement! .. + ton of things you could do to make this world a better place.. please just don;t waste it on another twitter app

5) Clouds are here to stay, what has to change is the way we look at and work with data + connected with 2) + a few old concepts ms thought about pioneering a few years back, maybe its time for - yet another - linux distribution, combining best of today's storage array internals, embedded systems, containers/vm technology and security(..). In combination with some dedicated (hopefully usb-sized) hw .. could be a interesting time-waster

SW + HW

1) Easy-to-use/build RF-net kits for low-bandwidth applications(irc/messaging fe) - pick a protocol/design your own, design a hierarchical topology of clients, ap's, retransmitters, keep an eye on per-country rf encryption restrictions and hope you'll never have to use it as your primary means of communication(eg no "accidents" on our main optic backbone)

2) HW keys to your cloud data/apps - turning your PC into an accessory/treating it the same like a cloud service provider with computing/storage services available based on the pc-os setup .. maybe the x-server architecture could finally become applauded ..

"HW" Only

1) The idea of public work-places is great! soldering sets, measuring gear, 3d printers, tools for lease, benches for alu/wood work etc - would probably be a hit anywhere(+ that equipment costs too much/takes years to gather at home.. ) - there is a hobbyist in most of us + in combination with a caffee/"fun" area/library and city funding, you may even get into some green numbers

2) In combination with 1) - electronics tuning shop - if you like to get your hands dirty(building hw slider switches into phones/nbs, custom cases/hw customization - router fw's etc) - you could get some traction if you;d presented your self as something underground/anti-establishment .. these days..

3) bio and localized farming - huge opportunities, really bad business models(we;re talking about real bio producers struggling with the rising regulatory pressure lobbied by the big guys, not the so-called bio farmers selling out to those big-co's) - monthly payments with 2x/4x a month "basket" deliveries of seasonal food to your doorstep with some it tech in the mixture + insurance coverage for the farmer +++ .. ok I'm hungry - sry for this half-baked not thought through / naive / unfeasible list and good luck ..