If you believe Apple's own (often vague) documentation, specifying properties in UIRequiredDeviceCapabilities causes filtering at Apple's point of delivery (app store). So if you specified 'wifi', in theory non-wifi devices wouldn't be able to install your app. However, all the iDevices so far support wifi.
Btw, UIRequiresPersistentWiFi does pertain to wifi directly in some ways. If you set this property to true, from my own tests I've seen that:
- while the application is running the wifi comms will continue to be available even after 30 mins timeout has passed
- if the app is running and wifi radio is currently timed out to 'off' (but wifi is enabled), first network access turns on wifi radio
- if the app is running and wifi is enabled, but user is not currently joined to any access point, network access causes a system prompt to appear to join one of the access points
Or, to put it another way: without this flag set, communication over wifi in your app can just appear to stop working. Or sometimes you can launch your app on your ipod or ipad and find that network comms is failing, even though wifi is enabled and you are near a good hotspot.
It's sad that Apple's documentation is so muddled and confusing.
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