Free tool to monitor and alert you with SMS, Email and Sound immediately when get PING consecutive loss <--> normal or TCP ports consecutive connection timeout <--> normal or CPU/MEM usage consecutive abnormal high <--> normal status changed. Alert you once only when the status changed, no continue sending you alerts when it remains abnormal. Let you know when is down and when is back exactly. Linux and Windows version.

• Ping_Alert : PING monitoring and alert. Alert you when PING consecutive loss and restored
• Port_Alert : Monitor TCP ports connection such as port 21 for FTP, 22(SSH), 23(TELNET), 25(SMTP), 53(DNS), 80(Httpd), 110(POP3), 1433(MSSQL), 3306(MYSQL) or any self defined port numbers. Monitoring TCP ports connection is monitoring those services. Article on ghacks.net for Port_Alert
• CPU_Alert : Monitor Linux / Windows CPU and MEMORY usage and send you alerts when CPU or MEM continues higher than pre-defined threshold and restored. Save the TOP1 program name and usage to log file whenever higher than threshold for you to pay attention earlier or capacity growth plan  
• SMSCMD : Windows / Linux command line send SMS directly. No installation required. smscmd "smscmd sending sms" "phone1,phone2"or input from file smscmd "text.txt" "phone.txt". Password file can be encrypted and put in local. Easy to be called by any types of program or put into Windows Scheduler or Linux cron table
• SMS4Mail :  Setup criteria to filter outlook incoming unread email's "Subject" and "Sender" then auto-forward to phones via SMS
• SMS4PayPal : Get SMS and additional email notification with detail transaction information whenever get PayPal paid or refunded. Easy to enable/disable within 2 minutes
• MailCMD - Windows command to send mail and attachment. No installation required and SSL supported. Response back with "Mail sent successfully with return code 0" or "Mail sent failure" for your program to take action. Also response back the attached file name and file size if there is an attachment