When applying the Power Attack temporary bonus, the app prompts for the applicable weapon, but none of the options include unarmed strike.
create a 1st level fighter
select Power Attack for the feat
add and equip a light weapon like a dagger
add and equip unarmed strike
go to Temporary Bonuses tab
add Power Attack (Light)
Note only Dagger is available to select.
Unarmed Attack would be ‘natural’ IIRC.
Okay, patch coming.