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With the 5n, I've found a manual flash triggered optically from the onboard flash to be a little less complicated than rigging up a wireless trigger -- I've done this successfully with a YongNuo 560, which is cheap (though not compact).
You should be able to do the same thing with the 7, though you'll have other options since it's got a flash shoe. There are a number of dedicated Sony units, and with an adapter, you could mount a wireless trigger to completely eliminate any onboard flash.
I don't use flash much with this camera anyway, but the ability to use an NEX-7 occasionally with a wireless trigger and remote slaves is pretty appealing.