I have owned four Bond Derringers and some extra barrels too. They are fun guns. Very reliable and you can change the barrels to shoot different calibers. I used to like to keep a .410/.45 Colt in my desk drawer or car center console. It was more of a single threat gun or used to fight my way to my regular gun.
Here is the problem though. They are heavy and big. For less weight I can carry a Glock 43, Kahr PM9, Sig P938, etc. in 9mm and have a lot more ammo at m y disposal. There size does not make the easy to carry. I had a few holsters for them but did not think they carried any better than most of my EDC guns, especially the Ruger LCP and Colt XSP, Sig P238 or even Sig P938. Their cross draw holster sounds good and looks cool but it does not conceal well at all. It is very noticeable that you have a gun under your shirt. They are pretty thick too.
For me they are Novelty guns. Good examples of the old Remington design. They also can shoot different calibers than most carry guns like .45 Colt.. .410 shotshell, 44 spl., etc. But you only get two shots. I would not feel well armed with just two shots. Having competed for many years I know that you can easily miss close targets under stress and in real life, those targets can move. I also learned from my two civilian experiences that bad guys often come in groups. The first time I was dealing with 3 men and the second time with two men. I had a 13 oz. .38 Spl +P in my pocket and felt safe. With a two shot derringer against 2 or 3 people, I would not feel very safe.
I think it makes a decent carjacking gun but so does a snub nose revolver, small .380 or 9mm. Even a small .45acp will make a good car gun. The Bond Arms guns are good snake guns. Load them with shot shell in a large caliber and you are good to go unless you are attacked by a snake gang.
They are not even good backup guns because they are heavy and bulky. I rather have a snub nose or LCP as a backup gun than a two shot anything. For some reason they market them thinking that have two big bullets will make up for have more small bullets. That is wrong thinking. First off a .22 to the head will stop a guy as much as a .45 to the head. A miss with a .45 is as good as a miss as a .22. Given that these small guns are difficult to shoot accurately under life and death stress, I think they are best used for fun guns. They are a lot of fun and as I used them, good for shooting up ammo you have for guns you no longer own.
If you want a small gun for a backup or even a bathing suit, take a look at the NAA mini revolvers. I sold my Bond Derringer for a NAA Pug with night sights in .22 magnum. It is a single shot too but it holds 5 and I have a laser on it. A .22 mag. is nothing to sneeze at today. They have hollow points that will expand with these small NAA revolvers now. You can even get one that has a swing out cylinder for faster reloading. This is what I use for a back up or to carry in a waterproof pocket of my bathing suit. A NAA mini revolver gives you absolutely no excuse to not carry a gun. You can hide it in a cigarette pack, tissue box, easily in a purse or pocketbook, and anywhere else. You can hide it in your hand as you walk through a dark parking lot at night. With a little practice you can learn to shot it accurately and fast. Add the laser to it and you have extended its useful range.
So there is my take on it and an alternate solution. The NAA mini revolvers come in many styles and are fun to collect. The Bond Arms are also fun but shooting the larger calibers from them is not fun for long. To buy a large Derringer in .380 or .22 is crazy because there are smaller/lighter guns that hold more of those rounds that conceal better.
That being said, I plan on buying another Bond Arms Derringer because I like to collect good examples of different types of guns. I do miss having my Derringer loaded with .410 shotshell in my desk draw or next to me wherever I sit. However, the new LCP II I got does a great job of that too. On the Plus side, a Derringer is safer to carry than even a DA revolver due to having to cock the hammer first. Then again the NAA is the same but just in a smaller caliber.