Which technology should we use?

We are planning to build our own trading system, assuming that the DB, SQLServer, trading processes and other components are ready.

What are the best technologies that we should consider to implement a fully responsive platform that can be used as a desktop, web and mobile (iOS and mobile) considering that there will be prices updates with SignarlR, and many other live updates, so the app has to be responsive and efficient enough.

And is it actually a good idea to build an app that works on all devices with a single technology ?