The popular task management app Wunderlist has been updated recently to support pro subscriptions. While the basic version of Wunderlist gives you free sync across devices, the pro version will let you create an unlimited amount of subtasks, assign tasks with other users for better collaboration, and more.
A Wunderlist Pro account is available as an in-app purchase. The actual app remains free as always. You can either choose to pay $4.99 a month or $49 a year. Along with the above mentioned features, you'll also get lots more backgrounds to choose from, the ability to share all your lists, and more. The activity center of Wunderlist will then aggregate all the lists you've shared and actions taken upon them.
A pro account is most likely ideal for those who need to collaborate as a team on lists and projects. For the price, it's not a bad option either. If you haven't checked out Wunderlist yet and you're looking for a new task management app, you can try out the free version and upgrade to pro in-app whenever you'd like.