I trade entirely off App, using TradeInterceptor.com works great, I have charts setup on left screen on the PC to watch, but still trade of ipad or android tablet, someone knocks on my door it goes with me. Dont like the idea of web page trading, my pc firefox and chrome crash to often, need a fresh windows install but can't be arsed.
Speed shouldn't be an issue if your logic is automated. The TT platform connects our phone apps direct to the same co-located servers as our browser based solution so your automated logic is running next to the matching engine. If you're trading trading a synthentic Autospreader contract, that trade logic in co-located. As we're running all of the logic on co-located servers, the local machine requirements are minimal. All of the heavy lifting is done away from the local interface. https://www.tradingtechnologies.com/blog/2016/03/15/a-look-back-on-tts-first-year/
Quite possibly there may NO free things to do. They may make money from interest from stock loaning, or possibly from restriction to phone only.