Do I need to root my phone to get a tcpdump? I'm troubleshooting my aCal installation and the good folks at aCal asked me for the output from tcpdump -A -- do I need to root my phone and install busybox or can I do this from a terminal emulator?
Yes, tcpdump is an administrator-level application (I highly doubt there will ever be an Android permission level to view all other apps' network traffic). Once rooted, if you have tcpdump binary (compiled for your device's cpu type) on sdcard, try:

su
mount -o remount rw /system/
cd /sdcard
cp ./tcpdump /system/xbin


Now you can use tcpdump command.

Without rooting, you could intercept traffic on your wifi LAN by setting a proxy to your computer in your device settings, and installing mitmproxy in a virtualenv on your computer and running it.