In my early days, I used various brands of detectors that worked pretty well. About 10 years ago I bought a Valentine, and find the arrows to be extermely useful- to the extent that I'll never buy another detector without the arrows or some similar feature. But the Valentine is hard to hide, mine is upper-right of the rearview mirror and the concealed display mounted in my ashtray; the main unit is still not concealed very well. I've tried mounting it in various places in the car (Corvette) or under the hood, they always reduce the range drastically, confuse the arrows, or both.
Are there any stealth (built in) detectors that have arrows like the Valentine, or some other way of telling you where the radar is coming from? I believe that some of them have a rear-facing antenna, but that doesn't do a lot of good unless there is an arrow or light to tell the actual direction.