Cheap NEX 7 wireless flash triggers
My understanding was Alpha flashes should work, but haven't verified.
Do you already have flashes? If so, I would try the ones you linked or get a Sony flash to standard hotshoe converter (Pixel Flash TF-325 appear to work on NEX 7 based on Amazon reviews) and use standard Cowboy Studio triggers.
If you don't have flashes, I would just get S2 flashes like TT520, TT560, or even ZE-DS12. These all have S2 slave mode. You need S2 mode so it fires when the main flash fires. If you get a flash with just a single slave mode, it will fire on the TTL pre-flash and won't work. With S2 flashes, no radio triggers are needed as you can trigger them with the built in flash.