show twitter stream from username

Hi there!
I've a buddypress site and I'd like my user can show their twitter streams inside my website.

I create a field and shows it properly,
but with the recently twitter API I'm not able to show the streamline just from the username my users provide.

I've created a widget inside twitter with my stream, but it has a code number and it seems it works only for my account.

Does any of you knows some way to do it
(without a plugin would be better)

Cheers