I wrote this post for Jmeter 2.8 this feature has been enabled by default for Jmeter 2.11 yippeee
If you want to get a status of how your Jmeter test is doing while it is running you can add the following Jsummariser. command line arguements when initiating a test.
jmeter.bat -n -t TestPlan.jmx -l results.csv -Jsummariser.name=summary -Jsummariser.interval=120 -Jsummariser.out=true
These attributes tell Jmeter that we want a summary during the test, output every 120 seconds to the screen.
This writes a summary output similar to the one below.
Every time interval Jmeter writes out the stats for the sample period on the + line and the cumulative for the test to date on the = line.
Obviously these are very high level statistics but they can provide confidence that the test is working particularly looking at the error count and an unexpected changes in throughput or response times.