Marco Polo works great, as does that Drone Mods cellular unit. . Just crashed my Inspire approaching 2 weeks ago ... signal suddenly went dead. First even near-crash in 500+ flights ... and just before a heavy rain started several hours later. Totally my fault (not DJI's fault) when I inadvertently dropped the altitude while making an S-turn using "Map View". Both actions are on the left stick and I must have inadvertently moved the stick slightly down when it was supposed to move this stick ONLY to the right.
I had a
Drone Mods cellular unit (about 50 grams) and a
Marco Polo locator (12 grams) mounted on the Inspire (behind the battery enclosure) at the time of the crash. The DJI Pilot app gave me a basic location, as did the Drone Mods cellular unit (showing the location on my iPhone Google maps), both within a minute. The
Marco Polo showed me a directional bearing, again within 30 seconds, all these while I was still at the "Home" take-off point. I immediately drove and then walked to the expected crash site (as guided by Google maps). However, in the many tall deciduous trees, dense vegetation, and Kutsu, I still could not find the Inspire, even with the Marco Polo, which was at this point giving me very strong signal-strength readings BUT started giving me confusing directional readings at the apparent site of the crash. ... That is, until I started pointing the Marco Polo directional locating transceiver/antenna directly up, triangulating from several different ground locations ...
and there it was, at 70 feet up, hard to see, engulfed in leaves, I found the Inspire. We eventually got it down before the rain started. Lesson

(1)
Don't crash your Inspire, because you will not get it back for 6-8 weeks from DJI Repair,

(2)
The Marco Polo (at no cost per month) and/or a
cellular tracker unit like Drone Mods ($5 per month cost)) are/is
a great insurance policy to get your Inspire (or other UAV) back, and

(3)
Don't forget to start the Inspire video recorder if you plan to crash (sad, because I really wanted to post the crash to this forum. It would have been spectacular if I had just remembered to push the record button).
In summary,
I highly recommend the Marco Polo, and/or, for more distant crashes, particularly if you lose the DJI Pilot app map location or it the Inspire flies off in the distance and crashes (or "emergency lands"), a cellular tracking device (Drone Mods ($5/month). Its worth this "insurance" investment for a $3400 drone. More info on request.
DJI Service - FYI: I was pleasantly surprised that DJI was very helpful in working with me after the crash. Other than the long turnaround time, which is a function of # of crashes vs # of technicians, I was pleased with their service and professionalism. Frankly, they have always been great to work with from my perspective, whether that be via the Technical Help Text "Chat" service of via the telephone help line. I know that others complain about their service, but I personally have had all good service and no bad service. Polite, knowledgeable, and helpful.