FringeFlyPost
I have been going regularly to the Edinburgh Festival Fringe and their app is always terrible. Connectivity is very spotty since the city is swarmed with way more people than usual and the older buildings can kill your signal. So I've been working on https://fringeflypost.com/, an event tracker with maps, search and filter, scheduling, and sharing with friends that's offline first. It syncs down a locally stored sqlite database and caches assets pretty aggressively. (You don't actually need to sign up, and you can just jump into the list of shows directly here https://fringeflypost.com/shows).