Interval Training with TomTom Cardio
I would think that it just needs an extra layer, ie:
Work > Time > 10mins > Pace > 5:00 - 6:00
Rest > Time > 2mins > Heart > Easy
or > Pace > 7:00 - 8:00
The watch could then beep when goes outside these Pace/Heart/Speed zones, and also when the interval changes.
I previously used a Polar HR watch that allowed these settings. That watch beeped fast/slow whilst you were outside the limits and then at the interval change, rather than just at the transition (as per the Tomtom).