Just received the Phoenix 0.45x magnetic add-on lens to replace the 0.5x I broke. I went out to test it and this is a sampling of the results. The lens attaches semi-securely even without the ring -- just don't jog or bump into anything. The ring will probably make it a firmer fit.
Can't believe how small it is compared to the other one I rigged up. Image quality looks better, too. Full range zoom with the lens on as well as close focusing. Nice.
Pictures of the setup are here: http://members.cox.net/visorblue/images/Phoenix045x.jpg
Still pictures with and without the lens are here (all shot in Auto P and f3.5):
Note: There's two models of the Phoenix 0.45x magnetic mount lens, large and small. You want the large one, 06-450 (P06450 at Amazon), the small one vignettes in still mode at full wide (17mm).