Not sure about "second handset concept"
The problem is do you get another SIM card/tleephone/number contract etc. for the lesser phone or do you swap the SIM card in and out all the time.
Swapping the SIM is just too much trouble and not an option for many females (and a few males) as removing/inserting the SIM card results in chipped nail varnish.
So in addtion to the home, office, mobile and fax numbers you already dish out you need to give out a second mobile number as well. This is also a real pain.
And if you are serioulsly worried about getting your phone nicked while in the pub just get the cheapo Motorola with a Tesco pay as you go deal. It wont cost much, no self respecting tea leaf would bother lifting it, and it will last forever.