How do i hook up my portable GPS system to my car speakers?

i have a portable GPS system, Mio c220. I cant really hear it that well so i want to hook it up to my car speakers. theres a headphone jack, im assuming u do something with that… BUT WHAT??? HELP
pertaining to GPS system hooked to car speakers

http://answers.yahoo.com/question/index;_ylt=ArkRN001LSJ7LD..uDTHEY3sy6IX;_ylv=3?qid=20070908162406AA9IBxw

i was thinking, is it possible to hook up the GPS system directly to my tweeters? – the little speakers near my mirrors. – They are not connected to anything right now.

I was thinking if i could buy one of those mini speakers that plug into ipods or mp3 players
like this
http://www.amazon.com/Coby-CS-MP27-Portable-Stereo-Speaker/dp/B000P1QYT0/ref=sr_1_4/102-2882929-7322503?ie=UTF8&s=electronics&qid=1189299943&sr=1-4

and then cut the wires, and just connect the wires to the tweeters.

would this cause any electrical shortages or problems??? would it even work? (stock 99 civic tweeters)

the gps system would be hooked into the charging cable via cigarette lighter as well

let me know!

and thanks!

OH and if u can email me back caffiendx27@yahoo.com thats where i get my emails!!!!

THANKS
i dont c aux interface?

http://www.oemautosound.com/c-152-honda-products.aspx