Hey, I'm with Mapzen, let me know if you have any questions. We're importing GTFS feeds from multiple transit agencies and serving them via a single API via our Transit.land project. We then pass the data into Turn-by-Turn, our open source routing engine which serves them up as data tiles. We select routes with on-the-fly costing and draws it via LRM (Leaflet Routing Machine).
hey eean -- that's on our roadmap! We can already route by bike, and by BART. Multimodal Bike+BART would basically look and act like the walking + transit directions we have now. Drop us a line at hello@mapzen.com and we'll let you know when it's ready.