I would like to store data using google protocol buffers (another serialized format would work, too), and then have an UI to browse that data. Is there a C++ framework/API that
Wireshark has a protobuf plugin that lets you visualize the contents of protobuf messages. I'd also dig in to the DebugString() in google/protobuf/message.h or message_lite.h (I forget which off the top of my head) and see if you can easily dress that up for presentation to a user.
http://code.google.com/p/protobuf-wireshark/