You're right to observe that a career as a security product developer is less open to embellishment through certification. In fact, I am unaware of any certifications that take a development rather than an operational approach. You don't say much in your e-mail about your educational background. Traditionally, the way to boost one's visibility and perceived value in more technical fields where certs are not available is to pursue an advanced degree like a Master's in computer science, software engineering, MIS, IT and so forth; if you already have a Master's, perhaps you might want to consider a PhD.
On the other hand, this is a reasonably active and in-demand area in the programming field. Are you sure that additional embellishment beyond a strongly and clearly worded recitation of your skills, knowledge and experience is necessary? I'm not convinced that your experience alone is not sufficient to help you grow and develop your career further. Perhaps it may be necessary only to keep seeking out new, interesting and meaningful development projects for you to grow and learn as you might like.
Good luck in your future career planning and development.
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This was first published in February 2003