While the "{STATE_AUDIOLEVEL}" token could be used to get the current detected input volume for the recording device used by the speech recognition engine, and that value could be used in a loop combined with a number of different actions to check the value, press the key, and provide a delay before the key is released, there are two main caveats to consider:
Because there is no buffer for the actual audio, you may find that the beginning of what you say is cut off, E.G. "hello" may come out as "lo"
The value returned by the speech recognition system (and thus, the token) may be too coarse to find a balance between not being so sensitive as to trigger on background noise, and being sensitive enough to reliably trigger quickly when you're speaking