Smartphone cameras are still getting bigger and better by the year, particularly if you look at high-end phones coming out of China with huge sensors and protruding bumps to match. These phones can deliver awesome results, and Im happy to use them in several situations where I would previously have had to rely on a dedicated camera. Just this week I used the Xiaomi 15 Ultra to shoot a Formula One event in Tokyo.But for all the advances that have been made, the laws of physics remain undefeated, and youre still going to get better results from a camera setup thats able to make use of larger lenses and sensors. Phones do need to be able to fit into our pockets, after all, so theres a limit to what can be achieved in that regard.At Mobile World Congress this year, some concept announcements showed that companies are thinking about this reality, coming up with ideas to move mobile photography beyond the constraints of the phone. The question is whether peripheral camera products can ever really be more than a niche curiosity.Xiaomis concept is called the Modular Optical System, and it involves self-contained camera modules that magnetically and wirelessly attach to your phone. While the company doesnt have concrete plans to sell them commercially, working models do exist I used one.The demonstration unit had a Micro Four Thirds-size sensor with a 17.5mm f/1.4 lens, which comes out to 35mm-equivalent when accounting for the sensors crop factor. It could attach to a Xiaomi 15 phone that had been outfitted with magnets and a window for laser data transfer but otherwise looked normal.The connection felt very secure, and there wasnt any need to fiddle with Bluetooth pairing or any special software once connected, the feed from the camera simply appears in the regular camera app. You can focus the lens by turning its ring or tapping the phones screen.Because the camera mounts to the middle of the phone, the resulting combination feels well-balanced and similar to a regular mirrorless camera. It did make me wish the phone had a dedicated shutter button on the edge, though; using the touchscreen with your hands in that position takes some getting used to.The results, at least as far as I could tell on the phone screen, were excellent. Micro Four Thirds is one of the smaller mirrorless formats, but its still a huge leap over even the 1-inch sensors found in the highest end phone cameras, and pairing one with a fast 35mm-equivalent lens makes for a really useful combination. I was taking pictures of friends in a dark restaurant that clearly could not have been captured on a phone.Realme, a sister brand to Oppo, took another approach. Its Ultra concept phone has a couple of traditional smartphone cameras as well as a third 1-inch sensor thats exposed behind the glass; you can attach a Leica M-mount adapter and a lens of your choice to use with that sensor.This feels somewhat less useful in practice. Theres no electrical connection between the lens and the phone, so adjusting the aperture ring isnt going to be reflected in software; the experience is more like adapting a manual lens to a digital camera.M-mount lenses are all manual focus, however, so there isnt a need for anything like the touchscreen AF solution like Xiaomi came up with. But the sensors 2.7x crop factor means that actual Leica M lenses will have a zoomed-in field of view even a wide-angle 28mm becomes a 75mm-equivalent portrait lens.These arent necessarily new ideas. Realmes is very similar to a Leica M-mount concept Xiaomi put out a few years ago, while Xiaomis own idea of wireless camera modules has been tried before.And Sony made a go of it in 2013 with the quirky QX line, a range of all-in-one cameras that connected over Wi-Fi and clipped onto the back of your phone; one model even featured an APS-C sensor and could work with any E-mount mirrorless lens. Olympus tried something similar in 2014 with the Air A01, a wireless Micro Four Thirds sensor and mount.There have been two big problems with these kinds of products in the past.The first was that they were a hassle to use, forcing you to deal with attachment mechanisms, wireless pairing, and slow connectivity. The appeal of mobile photography is its convenience, and these detracted from that.The second, arguably bigger hurdle is simply that they were separate devices that you had to carry alongside your phone. Thats a big ask for most people. Sonys QX100 had the same sensor and lens as its excellent RX100 compact camera, but it cost almost as much why not just carry the actual camera instead?Sony discontinued the QX line pretty quickly, suggesting it didnt take off with consumers. Things could be different today Xiaomis magnetic mount solution is certainly more convenient but its still hard to see the idea becoming mainstream.Personally, I would be interested in buying something like the Xiaomi concept I used. Id still have several questions, like how much itd cost and how long the magnetic mount would be supported on future handsets, but even in prototype form the idea worked well enough that I could see the extra lens being worth tossing into a tote bag.But for most people, my sense is that it will still be worth paying more attention to built-in phone camera quality for the foreseeable future. Thats the camera youll actually find yourself using.