Well, I wonder what this program might do!
It takes a PCAP file and will print the key headers of the IP + TCP/UDP headers. Anything else is binned, although that would be easy to add in.
You need libpcap to compile against. Compiling is done as follows:
gcc pcaptojson -o pcaptojson -lpcap
run as follows:
./pcaptojson -r
cat packets | ./pcaptojson
Hope this is useful. Feel free to do whatever you want with this software. A mention is always nice, but don't come looking for me if everything explodes and catches fire :)