Code Review by Codementor - Get an expert to review your code on-demand
DeepSource - Automated code reviews with static analysis.
Codebeat for iOS - Automated code review for iOS
Codacy - Automatically reviews code style, security, duplication, complexity, and coverage on every change while tracking code quality throughout your sprints.
CodeStream - CodeStream helps development teams resolve issues faster, and improve code quality by streamlining code reviews inside your IDE
Code Climate for Java - Code quality and test coverage for Java