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I use a WiFi router that supports a USB modem as an alternative to a wired connection to Internet. For mobile WiFi access, I use my phone as a WiFi router. The limitation for using a phone is that many smartphones only support the AdHoc mode. This is not a problem for laptops, but some eBooks readers only connect to a WiFi network in Infrastructure mode.
Addressing retail kiosks and oil pipeline mobile sites are different scenarios. For retail, use the services of a wireless Internet service provider, such as CLEAR, or the option recommended for oil pipeline mobile sites, which is using the services offered by your existing cellular/wireless carrier.