You can automate the use of SQL Profiler (also called Trace) either by using the correct stored procedures (sp_trace_create is the first of many, look 'em up in the BOL) or by setting up the trace that you like within SQL Profiler and then generating the scripts from there. Either way, assuming you collect just the default information, which will give you want you want, you won't place much of a load on your system. If you add tons and tons of counters, you can bring the system to it's knees. Start with the defaults and make adjustments as needed.

Since you're operating in 2005, you can also take a look at the Object Execution Statistics report. It doesn't tell you who called, but you can see quite a bit of other information. This gathers information from the dynamic management views such as sys.dm_exec_query_stats and others. You can look at those directly if you like.