Lookout's Wipe feature can erase all data on your device.
For all data to be completely erased, Lookout must be a Device Administrator.
- Open the Lookout app
- Choose the Menu button
- Tap "Settings"
- Scroll down check the box next to "Device Admin"
This will allow for a complete Wipe of your device (the same as a factory data reset) including the SD card (for Android OS 4.3 and below). See here for how to Wipe a device.