Q:

sniffing http headers on an embedded device

Is there any light weight tools which can filter and output http headers/responses in human readable form?  Something like wireshark.  I have tried tcpdump; but it is hard to read. 

A:

If you able to configure proxy settings on the embedded device you can (like in web browser) you can be very flexible.  I like for example Fiddler tool http://www.fiddler2.com/fiddler2/. If you start fiddler tool on you "normal" computer with Windows 7/XP etc, fiddler runs as a proxy with a port (typically 8888).  If you configure on the embedded device IP address with this port as a proxy, you will see or be able generate auto-responses etc.  inside of fiddler of your computer. 
So you can solve the problem without installation on embedded device any software. 
I don’t want to write a long text here, but I recommend watching video http://microsoftpdc.com/Sessions/CL25, where Fiddler developer Eric Lawrence explains Fiddler’s features.