The following are some of the known uses of Wapp in the wild:
The checklist application used to manage testing and release of SQLite is a Wapp script. Source code for the checklist application is at https://sqlite.org/checklistapp.
The search feature on the SQLite homepage is implemented using a Wapp-script, seen here. (NB: The search.tcl.in script is processed using mkscript.tcl prior to being deployed.)
The TCL-driven tests for SQLite have a Wapp-based interface that shows the testing progress. To see this interface in action, get a copy of the SQLite source tree and run:
configure make testfixture tclsh test/wapptest.tcl