My thoughts exactly! I easily get less than 60 calls per hour so this would be perfect. Interestingly, the caller ID for my number is tied to the first owner of my account before it was transferred to me (which happened many years ago).
Also, there are many applications in the market that does exactly this. I haven't installed any of them since I basically don't trust anyone with "read/write contacts" and "full internet access" at the same time (perfectly valid permissions for apps like this, but that doesn't mean I trust them).
A search for "vemringde" gives you four apps that targets Sweden specifically (so they are probably quite useless outside of Sweden), one of them mentions that it only works while having a 3G connection.