I used my cell phone and a Cass Creek Power horn speaker ($40) for two years before I bought a Foxpro Spitfire. Worked great and called in lots of critters.

Very nice!!!
in the small game forum on this site is a link to where I got the calls I use. The 30 minute call doesnt do squat. In fact I see NO animals with it. However the 7 second cottontail call is amazing. Ive called in a lynx (yes it was a lynx) and even a red tailo hawk with it. Ill be keeping that for next year!