Goodness me, I would love to get my hands on these!
You can get black, Christmas sets (red and green), 10 colour sets... and there are some amazing pictures of how very clever people have used these. One of my favourite examples is the decorated cookie.
I particularly liked the post about drawing on hardened fondant to make themed cupcakes (post here) but there have also been a number of posts about using the pens to decorate marshmallows (post here). I love how simply you could decorate a cake or cupcake and really make it something special with these pens, some corn syrup and some sparkles!
Now to find somewhere to buy them in Australia...