Tool or script to receive load average alerts?

Hi, what tool or script do you recommend to monitor the load average and cpu usage where I can receive email alerts. So to mitigate possible attacks ddos. help me please, recently I had a very high load and detected attack by netstat, already solvent, I have installed CSF pluign and some connection limits in ip tables, currently additional active mod_evasive in easyapache4. What do you recommend?