Simple - ALL aircraft have this feature built in and it costs not a single solitary penny.
Take-off set autopilot to chosen enroute altitude/heading/speed and goo and watch tv for the duration of the flight.
Approaching the destination, descend using the altitude setting, slow down using the speed setting and direction using the heading setting. Tune VOR1 to ILS of runway, set altitude to descend at a rate consistent with being at the runway altitude as stated in flightsim and slow down using speed setting and wait until the aircraft shows the ILS IDENT and then switch to APP mode and sit back and watch the aircraft land AUTOMATICALLY.
Now the ONLY aircraft this will not work with are those which don't have a radio stack and/or autopilot.