No more walking! Well, less anyway. We’ve all seen the millions of miles of fenceline with grass growing under it and mowed grass to either side. Maybe you’ve seen one of the guys walking the fenceline with a string trimmer — they walk fast since they don’t need a manicured look, but it’s still a long trip. The Postmaster looks to me like the end of that problem: Hook it to anything you can ride (it features a cotter-pin-type hitch) and watch it bump and swing around every post.
Don’t worry about hitting posts with it — the head is set up so it’ll swing straight behind you under pressure and swing back under the fence when it gets past the post. It might work for trimming under hedgerows as well.
Street pricing runs $600 — you might need a lot of fence to justify the purchase.