Yeah i hear "i tell you", "you know" but I have always heard it used when somebody is excited or passionately speaking of a topic.
Example.
A: kyou watashi ha kakkoii kuruma wo mita yo! Today I saw the very cool car.
B: maji!! sugoi ne.... Reall?!! amazing huh...
A: un! chou chou kakkoikatta yo! Yeah, It was very very cool!
Ex 2
A: OI! soko de sore wo shitenai kudasai! Hey! Please don't do that there!
B: ee! nani, nan to iimashitaka? huh? What, what did you say?
A: OI, Nande kiitenai yo! Hey, Why don't you listen!