[Mr_I]

We use a Windows app that we (okay, I) wrote some years ago. Students enter their ID numbers, and it logs when they sign in or out, displays who's currently in, keeps track of total hours (or hours over a given span of time, like Build Season), etc. While not typically required, I even let parents / mentors use it to document their time / volunteer hours for their employers.

(A neat feature to encourage students to accurately log out - if it detects a work shift of more than 10 hours, it flags it as "suspicious", and records only 1 minute of time. The admin then can declare it valid and record the full time, or adjust it to a more realistic log out time. 8^)