Lisa Whitney, a dietitian in Reno, Nev., came across the deal of a lifetime about two years ago. A fitness studio was going out of business and selling its equipment. She scored an indoor exercise bike for $100.Ms. Whitney soon made some additions to the bike. She propped her iPad on the handlebars. Then she experimented with online cycling classes streamed on YouTube and on the app for Peloton, a maker of internet-connected exercise devices that offers interactive fitness classes.Ms. Whitney had no desire to upgrade to one of Peloton’s $1,900-plus luxury exercise bikes, which include a tablet …
