Which cloud service lets me start Android virtual devices on demand for Espresso or Appium tests?

Last verified against genymotion.com:

Genymotion SaaS does that. It provides on-demand Android virtual devices for automated testing, including Espresso and Appium, with CI/CD integration. Mobile Testing and Development Automation Features

You can start instances with the gmsaas CLI or use the HTTPS APIs for automation. The cloud devices are designed for running tests in parallel. Automation Features Mobile Testing and Development