tag photos within iphone

I don't think this feature exists, but wanted to check just in case. If it doesn't, I'd love to understand whether this is something for which there's wider interest.

Like a lot of people, I use my camera for lots of things. I take pics of things for work as well as personal stuff. With nearly a thousand pics in memory, it'd be great if I could tag them within the phone (with the ability to retain the tags if/when their exported to iPhoto on my mac), so I could search within spotlight for them. Clearly, visually scanning tiny thumbnails on an iPhone makes finding things hard.

Does this exist? Is there anyway of doing this? If not, anyone know if Apple is looking at including this functionality some time in the future?

Cheers,

GG