I wasn't able to find a way to list the features in the Shapefile like you can list the Shapefiles in the Data Frame.
Taking the important parts from a larger script:
import arcpy
from arcpy import env
import os
activeoutputfolder= "C:\\Users"
mxd=arcpy.mapping.MapDocument("CURRENT") # The active Arcmap file
df= arcpy.mapping.ListDataFrames(mxd,"")[0] # "Layers"
lyr=arcpy.mapping.ListLayers(mxd,"",df)[0] # first thing in "Layers"
#------kmz export part
for x in range (0,3):
namea= arcpy.mapping.ListLayers(mxd,"",df).name
outputfile= str(activeoutputfolder)+"\\"+str(namea)+".kmz"
inputa= arcpy.mapping.ListLayers(mxd,"",df)
arcpy.LayerToKML_conversion(str(inputa), str(outputfile), "0", "false", "DEFAULT", "1024", "96", "CLAMPED_TO_GROUND")