you wont find a scanner that can change live data...but if you mean real-time than yes thats what you need. the l1sm is perfect, but they dont make em anymore. it is a software ran through a palm pilot. very good scanner and very portable. watch the classifeds at club gp they typically go for 150 or so. the auto tap is nice as well. they are a bit pricey, but has very nice software. you need a laptop to run it though.
you can order and install a 1.0 pcm (dhp/zzp/shitense) but they are generic tunes, and are probably good for your car (I/E/P) but to have a good tune you will need to adjust different fuel and spark tables to your cars likings, because each car is different. a zzp 1.0 pcm is a good start, and with a scanner, you will probably be ok, but a tuner is best