It probably already exists, but you could write a telnet that simply displays ASCII and hex side-by-side. I used something like this when I used to reverse engineer laboratory device control protocols (but it was a hardware implementation: http://www.atecorp.com/ATECorp/media/ProductImages/R/HP-Agil...)
tool already capable of doing it is socat.
ex: socat -v -x - tcp:google.com:80
add >/dev/null if you want do discard plain text output.
also works over ssl:
$ socat -v -x - openssl:google.com:443,verify=0
Not to mention wireshark...