This app was mentioned in 1 comment, with an average of 6.00 upvotes
In order: 1 - This is already a thing, supercook is the best I know and has an app. 2 - Again, already done, Australia even has official government public transport apps. 3 - Most big sales sites have suggested purchases, and unless the connection when more automated than they suggest then suppliers wouldn't use it. 4 - You'd be keeping track of large amounts of medical data, so you'd want to, at least, be a big company that can afford the security to keep it secure. It could be a thing, but not by someone who posts on reddit for feedback on app ideas. 5 - This is already a thing, most makers of devices that can connect to a phone have their own, there's plenty of generic ones that connect to all your devices. So the only way to really innovate would be to make it better than anyone else or to connect it to some physical device which augments the functions to make it work with lower tech things like a kettle or an old aircon, but then you're not asking about an app, you're asking about a device that would have an app attached to it. 6 - This could be interesting but would be very niche, good luck getting enough of an audience to keep it going longer than a month or so. 7 - A) technical difficulties of figuring out the brand name. If you're a genius who can get this to work reliably (or you don't be fuckin retarded like teks is and have them type it in) then B) you'd reach the loop conundrum, which is when to do A, you need B, but to obtain B, you need A. In this case, to get users, you'd need ratings, reviews and such, which you need users for. You could attempt to avoid this by 1) filling in as much as possible with reviews from you, friends and family, and 2) finding another review site that would let you share their database. But overall it'd be a nifty idea. I'd probably suggest this one if you were to do one. 8 - This is retarded, it never even says what it would actually do, they write it like they expect one person to give a portion of their battery charge to another, which is retarded. If you scrapped their entire idea and kept the name "Charge sharing app" a much smarter, more logical and, above all possible idea presents itself so obviously it makes me worried for Teks writers' ability to breath, and that is an app that lets you request to use a charger from nearby. People could have it open (come and charge as long as you want, put it on a time limit (maybe X% charge or Y minutes) , have it request only (then let the user send them a message to request charge access) or even try monetising it ('Stuck with a nearly dead battery? Use a little bit of that battery to find a charger near you, sure it might cost a couple of bucks but you can charge to 50% and be on your way' and you take a cut). 9 - This already exists, in a much more general form, that's also sooooo much better, in so many different instances that I can't even think of a "best" one to list as an example so I just looked up "app that finds picnic spots" on duckduckgo and I found this. 10 - Tinder, any dating site, any of the less well known alternatives to tinder. 11 - This idea would be pretty cool, I'm going to try to make something like this actually. Only smart one on here so far. 12 - Pretty sure this already exists, if it does/will it'd be gimmicky and boring, but it'd probably get fairly popular by moms who want to be hip so go ahead, you might get it somewhat popular. Just make sure you include a way to add it to instagram as well as social media 13 - This is just plain stupid. Literally any country where you're likely to both A) have a smartphone and B) care about clean neighbourhoods, already has local government bodies tasked with keeping it clean, and they all have phone numbers that are easily found. Also: why is it "best built for the iOS platform"? That makes no sense at all and no supporting reasons are given. 14 - This is honestly the most retarded idea on the list, they say "it'll be an improvement over weather forecasting apps" and then suggest a worse version of a weather forecasting app. 15 - 'Quit smoking apps' already exist, the idea of showing the extent of the damage is pretty interesting, but A) it'd be almost impossible to actually get it accurate because, you know, genetic differences, and B) noone would put that much effort into typing what sort of cigarette they had, so just stick it to filtered/non filtered and maybe a few general options, also C) there are numerous things which both aggravate and mitigate the effects of smoking, so if you wanted to be halfway accurate to the average effects, you'd need to include these, which you won't, because 1) more work than a lot of movies, 2) people would put even less effort into this bit than into what cigarette they had and 3) people wouldn't successfully do it even if you made it, they wouldn't realise all the things that affect it and wouldn't want to type it in for everything anyway.
So the ones that are worth thinking about in more detail are: 6, 7, 11 & 12. Those are the only ones you should even bother asking people for opinions on.