I'm looking for a cb plugin iframe too
so i worked and i made a plugin myself
i don't know if installation is ok but there is a zip file contains all necessary files.
if there are no tab found in cb, please execute these sql queries (501 is a default plugin id, change it if you want

also 25 is tab id, change it)
[code:1]INSERT INTO jos_comprofiler_plugin
(id, NAME, element, TYPE, folder, backend_menu, access, ordering, published, iscore, client_id, checked_out, params)
VALUES (501, "Iframe Integration", "iframe", "user", "plug_iframe", "", 0, 100, 1, 1, 0, 0, ""«»);
INSERT INTO jos_comprofiler_tabs
(tabid, title, description, ordering, ordering_register, width, enabled, pluginclass, pluginid, FIELDS, params, sys, displaytype, POSITION, useraccessgroupid)
VALUES (25, "Newsletter", "", 102, 10, 1, 1, "getIFrameTab", 501, 1, "", 1, "tab", "cb_tabmain", -2);
[/code:1]
If installation failed, please decompress zip file into [components/com_comprofiler/plugin/user] directory and execute queries
Enjoy, and say me if it's all right for you
Attachment plug_iframe.zip not found
Mick
ps: sorry for my very bad english