Find an android-core.zip file under the Processing.app folder (it should be somewhere in the modes/android subfolder).
Unzip this file into another folder. You can call this another folder anything. Lets say "android-core-new".
You will find batch of .class files in this unziped folder - those are the core processing classes (processing.*).
Now unzip oscP5.jar file into the same folder. By doing this we are adding all the oscP5 classes to the set of processing core classes. After this step, we need to zip everything again:
zip -r ../android-core-with-osc.zip *

Now we need to rename the old android-core.zip file to something like android-core-original.zip and rename the new android-core-with-osc.zip to android-core.zip so that Processing picks up it as its core library.

That`s it.

     [echo] Running zip align on final apk...
     [echo] Debug Package: /var/folders/Ub/Ubx6N2U8EWeUCPbYJ7KSoE+++TI/-Tmp-/android1706105251410438287.pde/bin/osctest-debug.apk
OscP5 0.9.6 infos, comments, questions at http://www.sojamo.de/oscP5
### [2011/6/21 18:15:38] PROCESS @ OscP5 stopped.
### [2011/6/21 18:15:38] PROCESS @ UdpClient.openSocket udp socket initialized.
### [2011/6/21 18:15:39] PROCESS @ UdpServer.start() new Unicast DatagramSocket created @ port 5555
### [2011/6/21 18:15:39] PROCESS @ UdpServer.run() UdpServer is running @ 5555
### [2011/6/21 18:15:39] INFO @ OscP5 is running. you (127.0.0.1) are listening @ port 5555
aha!
wooooooooooooow!
aha!
aha!
yeah!
aha!
yeah!
aha!
yeah!
yeah!
yeah!
yeah!