if all you want is to detect things like when you collide, you can add a child game-object with a collider that's set to a trigger and use that to fire off events such as when you've hit a wall or soemthing like that.
though, if you are going that route, keep in mind that the stock "TRIGGER ENTER/EXIT/STAY" events hard-coded into playmaker will fire off whenever they are met regardless of what you're colliding with is tagged... so, it's one of those "detect all the things" kinds of transitions... if you need some finer control, you could use your own defined events to use as transitions and use the trigger actions that come with it... so, if your wall is tagged as "wall" and you don't want this to fire off when it hits a projectile or another ship, you'd tell the trigger event to only detect "walls" and fire off the action.
And also... one thing to consider... trigger enter, exit and stay are all for different functions as you can expect but the trigger stay is sometimes the more responsive since it will detect what's in the trigger rather than what's entering it... so, if you have a "wall" that spawns right where the player is, if it's only looking for trigger enter, then it's not going to fire but if you have it look for trigger stay, then that's going to fire.
hope this helps a bit.
