If you REALLY want to attach it to your key chain then get a phone-charm cord like this.
Like the others I strongly recommend NOT putting the fob on your key chain.
I put mine in a zipped up pocket in my jacket so the jacket becomes my key.
If you ride in the rain a lot, then put the fob inside a sealed ziploc bag and then put it in a zipped pocket.
No jacket, no ride!
I love it when people watch me walk up to the bike fully dressed (lid on, jacket zipped up, gloves on) get on, start her, and just ride away.
You can see their disappointment when you DON'T have to take your gloves off, fumble around in pockets to find the key, then put gloves back on again like they would have to.
I love KIPASS!