Kerrie left a comment on my last blog, asking whether the Kangaroo Apples are edible, so I thought I'd answer here rather than there.
Kangaroo Apple is in the the Solanaceae family and other members of the family are vegetables (peppers, potatoes, tomatoes, capsicums), and potent extract producers such as tobacco and deadly night shade, as well as some Aussie bush tucker plants (desert tomato, desert raisin and kangaroo apple).
Apparently the aborigines around here treated the fruits of the kangaroo apple with respect, eating them only when they were very ripe. I've read that they can be a substitute for tomatoes in relish or chutney, and dried like dried tomatoes, used on pizza, but I'm a bit wary. As soon as I saw the word 'nightshade' in the same sentence as Kangaroo Apple I decided to leave it (eating the fruit) to the experts. It's a pity really, because they look quite tempting. Read more about it here - http://asgap.org.au/APOL34/jun04-5.html
and here - http://www.theoutbackcafe.com/?id=6&nid=40