The most simple solution to portable WiFi is your phone. With your phone, you can create a WiFi hotspot to share your mobile data. There is also a solution you can buy, like something called a MiFi router. A MiFi router is a mobile WiFi that can take a sim card and create a WiFi hotspot for several devices to connect to. Typically a MiFi router also comes with a battery. A good MiFi router can hold up to 20 hours before needing a recharge.