I'm not aware of any interfaces that work in conjunction with Track-it but I'm not a BMC employee either. One thing I can suggest, if it's possible, is to have your application send an email to the email monitor and have the ticket updated that way.
Brodiemac is correct. There are no published APIs or web services for Track-It!
I have seen other customers use the email option suggested and by setting up monitor policies to route emails certain ways depending on key words contained in the email messages, have made some interesting integrations between Track-It! and other systems.