I want to record my guitar using my phone. I found these soundhole pickups. If I convert the end to plug into my phone(directly, from the soundhole to phone), will it record the sound while I am using my camera?
Yes, it should very definitely be possible. The microphone input is the part of the sleeve closest to the cable, with ground being the second "ring" (and headphone left and right being on the "tip" of the 4 pin 3.5mm connector).
If the output impedance of the microphone (which the pick ups are, in principle, in the sense that they convert vibrations to electric signals) and the cell phone do not "match", you have to add additional components in line. As far as I remember my own experiments/reading, the source impedance should be considerably lower than the sink impedance. Also check out this question: https://electronics.stackexchange.com/questions/6846/how-important-is-impedance-matching-in-audio-applications.
Note that I have not tried this, and if you fry your phone it is your own fault/problem (try it with your cheap landfill 'droid that you still might have lying around somewhere).
Remark: I had some moderate success (waaay back when) in using a sound card as a makeshift oscilloscope, without blowing everything apart - so that might be yet another use for our personal computing units we carrry along everywhere...