Textbroker (www.textbroker.com) is another one of those rare sites that has employers that do not specifically hire their freelancers.
Like Mechanical Turk, you see an assignment that you like, you put your mark on it, and you do it. The employer then decides if it likes your work or not.
As can be guessed by the name, Textbroker is all about text, that is short articles on various subjects ranging from Business to Games to Travel to Weddings. Most, if not all, of the employers on Textbroker use it for blog posts, homework assignments (every freelance site has people that are obviously trying to pay someone to do their homework), book chapters, and other filler material that is written.
What's interesting about Textbroker is every time you work on an assignment, you're graded. Your grade, which can be two, three, four, or even five stars limits the assignments you can get. Naturally, the higher paying assignments are the five star assignments.
Each assignment tells the freelancer specifically what they want and a minimum word count. While writing a thousand words for an assignment that only wants 500 won't get you more money, it could increase your rank within Textbroker, especially if those thousand words are excellent and on topic.
When a freelancer selects an assignment, they are given ten minutes to accept or decline the assignment. Each assignment has specific SEO terms that the employer wants spread through the article several times. The timer for completing the work ranges from ten minutes to several days. Be sure to check the time limit. You do not want to be in the middle of a five hundred word assignment only to find that the time limit for it is ten minutes. While an essay that long can be written in ten minutes, it's not going to be a pretty essay.
Unlike most of the other entries in my list, Textbroker does not have a mobile app, though if you can type on your phone, you can just use the site.