The description is a bit fuzzy - does it only calculate how long it will take before you go oom? What I am hoping it is doing is calculate a mana burn rate and when you switch into viper, it will remember this number and provide you with an increasing timer. So with a mod like
TimeToDie - Addons - Curse you could simply viper until the two numbers match, then switch over to dragonhawk. With only
TimeToDie - Addons - Curse I never really have any problems estimating if I will go oom or not and even if I am unsure, often I will only be oom for 2-3 seconds at most and in that case I doubt it's even worth going into viper.
If you could somehow incorporate both addons into this one somehow, that would be absolutely superb.