A very interesting acquisition announcement from Twitter today: it’s buying Cover, an Android lockscreen app that lets you customise what apps you see and when. For now, Cover will remain live in the Play store.

“If that changes down the road, we’ll provide another update here,” the founders Todd Jackson, Gordon Luk and Edward Ho note in a blog post announcing the deal.

You can read Josh’s review of how Cover works here.

Cover is being somewhat cryptic in discussing what it will be working on at Twitter. “Twitter, like Cover, believes in the incredible potential of Android,” they write. “They share our vision that smartphones can be a lot smarter — more useful and more contextual — and together we’re going to make that happen. We’ll be building upon a lot of what makes Cover great, and we’re thrilled to create something even better at Twitter.”

At the same time, when you consider the work that Facebook has done in developing its Home service around the Android lockscreen, it’s clear that on some level, if an app is not owning the SIM that controls the entire phone, or the operating system, this is one very obvious way to remain front of mind for a user and incorporate a series of services that become front and center features for a user.

Apps are an overcrowded game. So owning the lockscreen gives you, effectively, a place to be first in the queue. It also gives Twitter some interesting potential routes for how it might longer-term try to deliver its stream of followers’ new and messages outside of its own app. Widgets featuring Twitter, Facebook, Pinterest and other streams are already quite common; Cover could work on ways to formalise and improve that experience.

It’s an area that others are eyeing up, too: Yahoo earlier this year acquired Aviate, which helps users customise their Android homescreens, for reportedly $80 million.

One question that lingers for me is how, when, and if companies like Twitter (and Facebook) will ever be able to think about these problems in the same way on iOS.

More generally, mobile has become a huge business for Twitter. Apart from the fact that Twitter was created as a mobile-first service, Twitter generates more in advertising from mobile than it does from desktop. Cover, meanwhile, says it has picked up “hundreds of thousands” of users since launching in October 2013.

To date, Cover had raised $1.7 million in funding, a seed round from First Round Capital, Harrison Metal, Max Levchin, Scott Banister, Charlie Cheever, Keith Rabois, Dave Girouard and Alex Franz.