Gmail Contacts "like" reference data management gui

Hi everyone, The system I am designing will need to be able to manage
some reference data. It would need a lookup and I really love some
sort of live search functionality, browse by groups/tags and a detail
where items can be added or updated. I quite like how you can manage
your contacts in gmail. How hard would it be to create something like
the gmail contacts management in Ruby on Rails? Maybe someone has
already developed something like that in Rails?