[xsmasher]

Careful! I've seen proxies (TracFone I think) subtly modify JSON files by removing whitespace, probably in the name of download speed. That will break the hashing.

If you start seeing unexplained errors on pay-as-you-go phones, you'll know why; although if this facility gains popularity then I'm sure they'll be pressured to stop modifying content.

[adrianmacneil]

This is not possible if you are loading resources over HTTPS (unless the carrier has installed a root certificate on your device, in which case you're not in a great place security-wise anyway).