Have radio items or checkboxes in your GMenu? Probably they’re effectively proxies for a key in GSettings somewhere.
Check out g_settings_create_action().
I write about this because someone suggested to me the other day that this may be a neat feature. I responded that I had thought about it before but never got around to implementing it. Clearly I had implemented it and just forgot. If I was able to forget that this exists, probably few other people know about it. Indeed, a quick ‘grep’ of my jhbuild checkoutdir shows very few users.