OK, here is the list of my ideas. "working" on it for years, never had balls to start implementing, BUT I am computer programmer if you want to work on any of those together, let me know. Otherwise take it, "steal it", and make it big. And mention you heard it from joe :)

- watches exchange club. you are doing as a middle man between watch lover. X amount to signup + monthly fee gives your user base access to each other watches. Users can exchange watches of similar value for X amount of time - like 3, 6 months. After that need to return the watch. Of course there is user verification system. Also each watch can be exchanged through a middle man (you) that will double check the watch quality before passing it forward to receiver (this would be at additional charge, something like Ebay Protect)

- whereabouts mobile app. simple app, mostly used by companies to track emps, but by parents as well. As simple as twitter, you just have access to someones up to date GPS location, not their messages feed.

- tldr (contacted tldr.com guy but never finished our talk). basically new version of digg. Let anyone submit article BUT other people can summarize it in X number of bullets and that's it. Nice feature -- other people can "fork it" - take that and edit it make a better version (shorter or longer with more info). Community votes on the best version. Articles/summarizes are linked with other articles in a time period that creates a story (like a news story that is developing).

- drawing together app. similar to draw something, but lets parents and children to use separate devices to draw together, or color cartoons, etc.

- iPhone door opener with patented technology. Develop and patent technology that creates a qr/barcode that opens the door (keys killer). that technology will work with different doors and car doors, etc. Obviously since no mechanical key is involved you can for example work for a company that uses this technology and instead of giving you physical keys, they can manage certain doors to be open with your phone.

- perfumania. not too much IT related but this idea poped to my head while working on fifth avenue. walking every morning millions of women pass me by. now, you have soda/chips vending machines, you can rent movies via machine. develop and patent machine to dispense either paper sticks or tiny containers with perfumes. a client has access to a wall of 50 or more different fragrances (perhaps some of a well established brands, but not only so client can discover new fragrances). sell it real cheap so each day a women can get sprayed with different fragrance.

- impressed by this thread: http://news.ycombinator.com/item?id=3748104 I registered thumbkissing.com Any ideas for app? - contact me.

- app for "display" shops. It was a nightmare to buy furniture for my new place. went through plenty of places and been buried under phonebook-thick catalogs. There must be better way. An app to browse shop offer via ipad. Develop app. Start with furniture, there is only couple main companies that shops get their supplies from. Upload entire offer; offer iPads cheap to shop owners as a medium to browse their inventory. My impression - they will quickly switch from thick catalogs that shows everything, not exactly what each shop has or can have on stock/sell. Repeat for other stores: mattress places, etc.

- better hacker news :) this one is still on my todo list. DO NOT change anything that currently is, just add more options: follow hackers (notified when they type new comment), remove comments, branches from long commend thread that you been reading, mark/hide read comments, notifier of number of new comments since you read last time, etc. Lock the website to 1,000-5,000 HN readers (registered users) not to kill/piss off PG that your boot is raping HN server.

- human protocol (I call it HAPI - Human Application Protocol Interface). Basically reversed interned when people push the data instead of pull. Hard to explain shortly here. Basically a stream where each task has its code and you pushing "strings" of data where others can read them. no website, just plain data. For example you want to sell a car? you push "status: 40 [selling], location: 4903 [New York], var1: 3254 [Model of car]" etc. Then users build receivers that treat this information accordingly, but stream on its own in uncontrollable, something like uploaded torrent.

- interests mailbox. I want to unsubscribe my personal email from all the "Spam" I am getting and have one mailbox that I can select the offers I want to receive. Imagine it the same way like when you changing your address usps gives you all the offers of local stores. if im interested in gardening, I want to be able to pickup "theme" gardening and signup for all the emails related to the subject from all vendors out there.

- twitter for businesses. same idea but you follow companies so the focus is on the tools for a company to promote and sell their products. Twitter is not the best platform for it; hasnt been designed for this purpose and does not provide unified tools.

- we are vacationing. I want a website where I can create our tour map that looks cool and all our friends can check on it. where are we, what we doing, where we been, of course uploading photos and videos on the way.

- fanBooth. mostly for cute girls. website when you can take only one shoot a day (or very limited number). of yourselves and other can "follow" you: put comments, etc. you can tag that photo like #tryingnewclothes. others can vote on the best for day/week/month in certain category.

- mallHunter. you seen all those little booths at your local mall? provide them with app when they can upload their items to sell: take photo and upload, everything they have on sale/discount.

- habitBreaker. website/app where I can mark the date that I quit smoking/drinking/doping and see other people that did the same and compare how many days I stay clean. Community can type message that keeps them away from the habit, others can vote on it "helped me too" and then the top votes are send via email blast or displayed on the website.

EDIT: vote up if you liked any of those :)