WTF !
How the hell do you get from "any modern smartphone already contains hardware capable of the job" to "As most Reg readers will be well aware, the cost of NextGen equipment could be insignificant in the context of aviation" ?
There is only one guarantee in aviation - whatever standards arrive, consumer electronics at consumer electronics prices will NOT be allowed. Just getting Mode-S for a light aircraft is non-trivial in cost terms - and just to top it off, the regulators (CAA in our case) then charge you for the privilege of being allowed to do it (this cost alone can be into four figures if it's not classed as a 'minor mod').
And while other parts of the world are busy installing modern systems to use the new capabilities - here in the UK, I understand there are no plans to provide any data whatsoever that might provide some justification for fitting the gear. The result is that in the US where Mode-S is not mandatory there are queues at avionics shops to get new kit installed (note - the US actually use the uplink capability to provide information such as weather), but over here where it's already mandatory for many aircraft we are busy trying to fight the imposition of costs which benefit only the commercial sector who then complain and try to claim that they are subsidising the small guys.