An app you would follow

So iOS users tend to love the quality and innovation of iOS apps, Android users praise the customisability of launchers and tasker apps and WP8 users enjoy the... erm... er... ah! integration with Microsoft services (phew!).

Most folk have invested a little in their chosen OS ecosystem; we buy apps and get used to the ways our OS works. In fact, the thought of moving to another OS can often bring an uncomfortable sense of dread - having to learn everything again? Having to find equivalent apps and systems? Oh boy. Ecosystems are designed to keep us inside. And most of us are happy to stay where we are just because of the fuss needed to swap.

So here is my question:

What app would you follow? If one app suddenly up and left your ecosystem and became a platform exclusive elsewhere, would you be willing to follow it?

For example, I would probably follow Youtube (Android) anywhere. I use it everyday and I love the design and the way it links so easily with Chromecast.

Rules

1. No 'Oh, but there's an alternative you could use'. Of course there is an alternative. But the question is asking what you would follow! :)

2. Follow rule 1.