Smart Labour (InstantLabour in versions of ServiceM8 prior to 4.0) allows your job labour to automatically be set based on your check in and check out timer.
To use Smart Labour:
Open a job on the ServiceM8 app
Tap Start Job to check in to the job
In the billing screen, tap Add Item/Service
Tap Smart Labour
Tap to select the appropriate labour rate from the list of labour items
Note: the items available to select in Smart Labour are automatically chosen from your Materials & Services database. Any materials with the word "Labour" or "Labor" in the name will be available to use with the Smart Labour feature.