Like Loader, BlazeMeter is an API load-testing service that provides real-time reporting features, plus other goodies like geo-distributed load testing (you can have traffic generated from servers on multiple continents) and support for tests created by Apache JMeter.
Sign up, and you’re given a 14-day trial of the Pro version (normally $649 per month). After that, you’re on the feature-restricted free tier, where you’re limited to 50 concurrent users in tests, up to 10 tests, a maximum test duration of 20 minutes, and data retained from tests for only one week. You do, however, get to use BlazeMeter’s Selenium Webdriver test suite, albeit for only five concurrent (simulated) users.