What are you using to test single-page web apps across mobile devices?

My startup (www.helpwith.co) is built on meteor.js, and we're having bit of trouble testing across different mobile devices and OS versions. Most testing software is either for conventional sites or native apps (not single page JS apps).

I've seen dozens of saas options out there for multi device testing, but there is too much noise in that space that it's hard to determine which option would be best for a pre-revenue startup.

I'd love to hear your experiences/ suggestions!