I think it was introduced as an option for model year 2016 cars when the MIB2 infotainment units were introduced, so cars built from (I think ) build week 22 in 2015. Car Net App Connect was an extra cost option; around £100 if spec’d from new. I think the current cost to have it retro added is around £250.
@titchy; if App Connect is a deal breaker for you, be aware that if the car you’re considering doesn’t have it, not all of the MIB2 infotainment units are App Connect compatible.