The closest to your BB interface above is the Nagios Service Check Acceptor NSCA. It accepts a plain text format on a TCP socket. Besides the binary send_ncsa there is Net::NSCA::Client, which I do _not_ know.

But keep in mind that pure passive checks are a bit at odds with Nagios' state polling philosophy. If you are not allowed to add an agent like NRPE or the excellent check_mk, you may consider check_by_ssh. Since years OpenSSH offers the ControlMaster option to re-use existing connections. Without the very expensive key exchange phase, the transfer performance is not much different from raw TCP such as with NRPE. It just needs a bit of thought with your templates to coordinate master and slave.