The Help Desk Website designed for eCoastNetorks (see: http://www.ecoastnetworks.com/) helps them keep track of all the computer and networking issues they have for the thousands of computers and networks they support amoungst their clients. In addition to replying to tickets by email, eCoastNetworks also has the option of recieving and responding to requests via text. They also use the system for logging time spent on each ticket that they import into their time and billing system.
Starting at $3,000, further customization is available.