In this edition of The Motley Fool's "Ask a Fool" series, Motley Fool Rule Breakers analyst Simon Erickson takes a question from a reader who asks: "Any insight as to where fuel cell technology is heading in the Fool's opinion?"  

Simon focuses on the recent hot streak of Plug Power (PLUG -3.83%), whose stock price has risen nearly 500% after the company announced deals with Air Liquide and FedEx (FDX -0.29%).  He offers two things that investors should keep an eye on, as well as his take on the stock right now.