MALClient is 3rd party app for managing your anime and manga list on MyAnimeList.net as well as accessing other website features.

It allows you to:
• Browse your own list as well as others'.
• Update your anime entries.
• Read anime reviews.
• Browse related anime.
• View top anime and manga in various categories.
• Search for characters!
• Check Character&Staff details.
• Read MAL News&Articles.
• View your watching/reading history.
• Watch promotional videos.
• Manage favourite shows, characters etc.
• Browse most recent recommendations.
• Build your weekly calendar with currently airing shows.
• Add widget with shows airing today.
• And much more!

Additionally it allows to access social aspects of service with features like:
• Forum
• Private Messaging
• Comment Conversations
• Notifications
• Friends Feeds
• Browse, join and chat in MAL clubs.

To top it off it's fully open sourced.

As for in-app purchases; they are all donations so don't worry about them :)