The trend to having a mobile game tied to the release of your AAA game is growing. Nathan Drake and the Uncharted series have now succumbed to the practice.
Uncharted: Fortune Hunter is a free-to-play puzzle game released for iOS and Android by PlayStation Mobile just in time for Uncharted 4: A Thief's End to hit next week. The game is a more cartoony take on the daring Drake's deeds on the PS4, and offers six chapters and 200 puzzles. Connecting to the PlayStation Network will allow you to unlock some multiplayer rewards for Uncharted 4 such as skins, relics and one-time boosters. Sully even makes an appearance.
The disclaimer mentions in-app purchases are available, but the aren't specifically delineated.
You only have a few more days for the real thing, though, as A Thief's End comes out on May 10.