Lenovo's Moto Z is by far the most promising start to the elusive modular smartphone currently in the market, and sets the stage for what such smartphones should be like in the future.

By itself, the Moto Z is a respectable flagship. But when you improve its functions by snapping on various add-ons - or Moto Mods - to it, the real potential of modular phones becomes apparent.

The Moto Z is a beautiful phone. It is thin, light and has a svelte grace other premium phones today lack, due to their bigger screens and chunky batteries.

Its 5.5-inch screen sits right in that sweet spot of having a large enough screen for enjoyable media viewing while still being usable with one hand.

The location of the fingerprint sensor, just below the Moto branding, is unfortunate though. It took me a while to get used to its not being a physical button, as I absent-mindedly kept pressing it to get to the home screen to no avail.

A huge plus point for me about the Moto Z is that it runs near-stock Android - local sets will come with almost no bloatware. Couple it with the powerful Snapdragon 820 processor and the Moto Z is a small but efficient beast, running resource-intensive apps with little trouble.

The real fun of the Moto Z begins when you mess around with the Moto Mods available for it. These mods are hot-swoppable - meaning you don't have to turn off the phone to change them, making it effortless to transform the Moto Z from a camera to a speaker or projector.

They use magnets to easily snap onto the back of the Moto Z and work immediately with no installation time.

The Hasselblad Camera mod ($459) is the most expensive module for the phone. Slap this on and it fundamentally changes the Moto Z's camera, adding a 10x optical zoom but also downgrading from the phone's 16-megapixel camera to a 12-megapixel one.

The zoom on the mod is really stellar. On test pictures taken at full zoom, subjects still appear in focus, thanks to the optical image stabilisation.

The JBL speaker mod ($139) is another one which can prove useful on occasion, such as when you really need to share your music and the speaker on the phone can't cut it.

But as speakers go, it doesn't really do much for audio quality. Music playback is noticeably louder with more body, but that's about it.

The mod's kickstand also props it up at an awkward angle, projecting the sound onto the surface instead of forward. This muffles the sound considerably, especially if you're in front of the phone and not facing the back where the speakers are.

What really grew on me after prolonged use, however, was the Moto projector ($399), which lets you project your screen onto a wall. Projecting YouTube videos onto my ceiling while lying down in bed is something I can get used to.

It's a pity the double-stacking of mods isn't possible, as slapping on the JBL speaker mod to use concurrently with the projector would help with the tinny sound from the phone's speakers.

I could, however, connect a portable Bluetooth speaker to the phone, resulting in a more pleasant viewing experience.

The fourth add-on, the Incipio Power Pack ($139), is just a power bank in disguise, as it provides 20 more hours of battery life to the phone. It could serve power users very well, as the Moto Z's default battery life is a little on the low side due to its smaller battery.

It's convenient and lighter than most power banks, though at a significantly higher cost.

•Verdict: The Moto Z sets the baseline for what modular phones should be like, and is a stellar phone that is boosted by the range of mods available for it.