Trackl is a time tracker app which has a dedicated reference field, next to a standard description field. The reference field is the “guide”: It can be configured with different regular expressions and colors. Even different issue types can be entered, such as Jira and Redmine issues.
The great advantage is that you have control over the reference field values, which can be used later for invoicing and other things.
Trackl is currently used as an internal tool at labsolution.lu. Feel free to use the contact form if you are interested,