Would you entrust a personal-injury claim, divorce settlement or high-stakes contract to an algorithm? A growing number of apps and digital services are betting you will, attracting millions of Silicon Valley investment dollars but raising questions about the limits and ethics of technology in the legal sphere. Among the leaders in the emergent robo-lawyering field is DoNotPay, an app dreamed up by Joshua Browder in 2015, when he was a 17-year-old Stanford University student, to help friends dispute parking tickets. The app, which relies on an artificial intelligence-enabled chatbot, became popular, and has expanded its focus to other consumer legal services. In June it hit the million-case mark, helping save people upward of $30 million since it started, Mr. Browder says. It raised a new $12 million round of funding the same month.