Interesting. I was actually thinking about this topic earlier today and made a post on Amigaworld. I'll just Cut&paste it here.
Pretty much every HDTV in existance contains a flicker fixer(scandoubler/deinterlacer). It seems like it should be an easy matter to make a cheap flicker fixer for any amiga. I've read that the 23 pin D-Sub connectors are hard to find? Couldn't something that plugs into the denise chip be easy to make? $170 for an external toastscan seems ridiculous. Even a cheap device that outputs S-Video would be useful.
Component video would be even better. My old DVD player outputs 480I (interlace) via component. My panasonic plasma TV then takes the 480I signal and converts it to 720P (native resolution). In effect, acting as a deinterlacer/scandoubler.
I live in the US, so SCART is pretty useless here.
The only reason I can see for needing a scandoubler/deinterlacer for your x-box, x-box 360, ps2, or ps3 would be to connect it to a computer monitor. I'm not sure why anyone would do that? Most people would rather play on a larger TV screen than even a 21" LCD Flat panel. You dont need a scandoubler/deinterlacer to play your xbox/xbox360/ps2/ps3 on a HDTV. You can get a cheap component, DVI, or HDMI cable to connect it to your TV and let your TV do the flicker fixing. An HDTV will even upconvert S-VIDEO to it's native resolution.