a) Any software will do, all it has to do is talk to the serial port. A popular choice is Processing, it is free and has a very arduino like UI and syntax.
b) For RF if you want two way communications you are best with an Xbee system.
c) See above.
d)
So it wouldn't be very smart so to speak
well it would have enough to do, any arduino will cope.
Does this make sense
Yes but refine the bit about the RF.