I am resisting the temptation to buy those lenses too: it's too cheap to be anything more than toys..
As for the tele, my guess is that by putting a bad quality 2x tele in front of your lens you might actually lose
the wide angle is different, as long as you take it as a toy.
1) bear in mind that their rating (0.5 x) are nominal and often very different from the real ones.
This quite honest guy gives you the real results0.45 wide angle + macro Canon A540 A560 A570 A700 A710 on eBay, also, For Other Cameras, Camera Lenses, Photography (end time 23-Jun-08 15:39:29 BST)
0.45 lenses are actually 0.60, this means that you expect a field increased by 120% and yhat you get is a mere 66% field more. not impressive... see the photo he gives
2) if you go on a stronger lens be ready to have a lot of chromatic problems,
From the same guy's shop, a stronger (and more expensive) lens:Sklep Internetowy foto-tip
(0.38x nominal, actually 0.45x)
Being an honest guy, he gives you the results you can get with these sort of lenses:http://www.foto-tip.pl/Galeria/galeria.htm
look at the first three photos:
top: normal shot
below left: taken with 0.6x lens (the first one)
below right:taken with 0.45x lens (the second one)
so, the first lens gives you a field that is just a little bit larger, nothing impressive.
the second one gives you so much chromatic defects that you can see them even in the thumbnail (top right corner). also, try zooming in and look at the stones in the bottom right corner...
But, if this is acceptable for you, and you take them as "toys", they can be fun anyway...