A few times, while playing Steel Storm: Burning Retribution, I've seen
"Press the storm plow to use the shockwave device!"
appear at the top of the screen for a few seconds, seemingly with no trigger, before disappearing. I've seen no other mention of storm plows or shockwave devices.
What does this mean?
Probably it's just a suggestion to use it.
Storm Plow is a weapon, you can acquire it in Mission 1 in the Born to Burn group.
Step on a trigger that will open the nearby force-field gate, allowing you to acquire the Storm Plow weapon
It's worth noting that if you perish before exiting the level, the weapon will be destroyed and you cannot reacquire it in that playthrough.
Source, Steel Storm strategy guide
