1.Warm up jog
2.Run hard for 40 seconds
3.Walk till pulse is about 140
4.Repeat 7 times steps 2 and 3
5.Cool down walk

Yeah.
Thats what I'm trying to encourage ppl to do.
go buy your heart rate rather than by a time. Its much more sensible.

Definately buy a heart rate monitor and monitor intervals that way.

Once you start to understand your body (and its upper limits) then you maybe be able to formulate a interval routine based on time, however this should be reviewed and varied often as you progress, and for the purpose of variation and keeping your body on it's toes.

I wrote an article here: » Monitoring your HIIT intervals - HIIT Source any feedback would be good.