Tag or message to GUI indicator

Hello,

May I ask what is the best way to visualize tags or messages in GR GUI?

For example: there is a head block with reset function that each time it has processed specified number of samples sends tag or message "FINISHED".

I am looking for a way this tag or message would affect a variable or some GUI element. Dumping tags or messages to terminal via debug block is quite neat , but is there any possibility to show all information in GUI (in a form of simple indicator: True/False or value)?.

I didn't wanted to employ any streams or sources triggered by tag or message to reduce resources utilization.

Kind regards,

Marcin Wachowiak