Some stats from mynearestmarginal.com.
I've shared this because it gives an unfiltered insight into what devices and browsers are used by Momentum's demographic. I would assume that this matches the demographic a lot of startups also target. That's an assumption on my part though.
Uses Node, Express, Handlebars for backend. jQuery and Google Maps for front end. MongoDB for database (and crucially geospatial search). Cloudflare and Heroku for hosting / scaling.