I built a Windows phone app for PAX that let you have the schedule and maps offline. At the time there was an iOS and and Android app, but not even an unofficial one for Windows. There are more apps now, and PAX has gotten more "professional" a.k.a it has gotten harder every year to access the schedule. This year it wanted me to log in to the Guidebook site to even see it and I decided that was a good cue to stop providing the app so when Microsoft said anything without an age rating would be unpublished i just let it happen (it's less necessary now anyway since internet access at PAX has gone from none-whatsoever to pretty decent). I had several hundred users each year, and people emailed me suggestions and requests. Definitely the only individual project I've ever done that had other people relying on me, and it was harder than I thought (one year MSFT didn't approve my update with the new schedule until after PAX, so then I built an in-app downloader that fetched the schedule data from my server, etc).