Sling TV, the Dish-owned online streaming service that promises live TV via the internet, has been plagued with one serious problem since launch: you could only stream Sling TV to one device at a time. Today, the company is attempting to address that issue with the launch of a new “multi-stream” service, now in beta, that lets you stream live TV to up to three devices at a time, both inside and out of the home. At launch, however, the selection is limited to a handful of networks owned by FOX, including broadcast channels (in some markets), FOX Sports, FX, and National Geographic, along with optional add-ons like AMC, A&E, HBO, Turner, Scripps, EPIX and Univision.These add-ons are available in the new service’s “Extra” packages, as opposed to shipping with the core offering which is priced at $20 per month. Similar to Sling TV’s original offering, customers can choose from add-on packages like “Hollywood Extra,” “Lifestyle Extra,” “World News Extra,” HBO and Cinemax.Add-ons are still priced at $5 per month, except for the premium channels which set their own pricing. (HBO is $15/mo and Cinemax is $10/mo).Local broadcast content, live and on-demand, is currently limited in the new service to 17 markets: Atlanta, Austin, Charlotte N.C., Chicago, Dallas, Detroit, Gainesville, Fla., Houston, Los Angeles, Minneapolis, New York, Orlando, Philadelphia, Pa., Phoenix, San Francisco, Tampa, Fla. and Washington D.C. However, Sling TV says it plans to add local content from FOX affiliates in the future on a market-by-market basis.But what that means is, for now, is that your ability to access broadcast FOX TV will vary as you travel.