A $2 video cable lets me record guitar and synth into my iPod Touch with the brilliant Everyday Looper app (mancingdolecules.com; $5.99).
Following a tip on my favorite music-app site, the-palm-sound.blogspot.com, I grabbed a $2.34 iPod video cable from monoprice.com to give my 2G iPod Touch an audio input. The cable has a 4-conductor (TRRS), 1⁄8-inch plug at one end and three RCA plugs at the other—red, white, and yellow. On some older iPods, the yellow RCA outputs video. On the iPhone and iPod Touch, it connects to the mic input. The white and red plugs output left and right audio channels, respectively.
This hack reportedly works on other smartphones, but it''s not perfect. The iPhone/Touch mic input has issues (bit.ly/MicSpec), and because it doubles as a remote-control input, my iPod started playing unexpectedly. I got much better results with the Peavey AmpKit LiNK ($39.99), which uses active circuitry to set tone and levels.