Have a look at mattdm's guide to flashes if you're interested in her having a totally automatic unit:
Pentax P-TTL Flash Comparison: The Definitive Guide
The *ist DS is also capable of taking TTL flashes where the newer dSLRs could not utilise it. This to allows for auto shooting, and you can find many of the older Pentax (and other third party TTL flash) units with TTL for much cheaper than the P-TTL flashes, which use a pre-flash to gauge exposure.
So a unit like the Pentax AF 240 or 280 or 400 flashes are TTL units that are affordable and very capable. Only they're not available new...
Hope this is useful for you.