Mac Low Disk Space Alert

Hi,

I have a Mac Mini which I installed a 128gb SSD.

Twice my Mac has failed to boot when it runs out of space resulting in hours of troubleshooting and trying to fix it.

This time around I didnt get any indication from OSX

Is there a utility which can alert me at say 90% and 95% full? I really dont want to go through that process again!

My SSD had mainly filled up with my iOS apps and iPhone/iPad backups. Deleting the apps freed up about 35gb space!