In reply to ianstevens:
> Lets think about how these two are essentially mutually exclusive for a hot second.
They're not though, necessarily, are they. There are lots of apps available that do much more complicated things than that and are properly free. (Though making a donation is usually an option.) Besides which the OP doesn't even want it to be free necessarily, just not expensive.
I would suggest "myWorkouts" - but I don't think it has the facility to set alarms for low/high heart rate.