As part of Pocket Gamer Connects San Francisco 2015, Francis Doumet, founder of Adenda, gave a talk about monetising users on their lock screens.
Doumet called lock screens "prime real estate", as they're looked at, on average, between 35 and 100 times a day by smartphone users.
Lock screens can be used for anything from fully interactive mini-games, to full page, rich content ads that deep link to a specific article or ad.
Doumet claims that "there's potential to earn $0.12 per day per user" from lock screen content, given the high frequency that users look at the screen, and growing interest from advertisers.
You can see all our videos from Pocket Gamer Connects San Francisco 2015 in this YouTube Playlist.