Reddit reviews iPhone 6 Plus Privacy Screen Protector - Fosmon [Anti-Spy] Screen Shield for Apple iPhone 6 Plus / iPhone 6s Plus (5.5")

Well, I dont understand why anyone would want to go on a public wifi, because the traffic is all going through Starbucks or whatever before it goes through to a ISP. If anyone can give me a solid answer I would be happy to hear. Obviously you may want to set up a reputation before you start the operation, choose a certain time and day or days, bring your laptop, order the same coffee every time, learn the staffs names, make them remember you. So you do not look inconspicuous or troublesome. Building the relationship is a key point because you would be hiding in plain sight. Next I would make sure you sit in a position in the shop that stops all cameras in the shop from seeing your screen, including window reflections of your screen. This shouldn't be to difficult, but finding a position that stops anyone from seeing your screen, making sure its hard for the person not to approach fast enough to not allow you to hide your screen. You could also use a ANTI-spy cover, an example
https://www.amazon.com/gp/product/B00PSSTGYU/ref=s9_dcacsd_bhz_bw_c_x_2

Only some quick notes that may help.