That falls in to the category of the "auto lockers" that I mentioned, and as mentioned earlier, I would avoid them in a daily driver, especially one used in winter. On a trail rig that sees occasional on-road use - go right ahead.
What those auto-lockers do, is local the half shafts together under power, and yes, they do prevent differentiation, so my earlier comments on that are applicable. They are supposed to unlock and allow one wheel, the outer wheel in a turn, to "over run" the inner wheel, whether or not that will actually happen will depend on how much power you're trying to lay down at the time.
Some of them, there are several different brands, can be quite finicky and almost all of them will click, pop and even bang when they unlock.
The real question you need to ask is when do you want the added traction - primarily on the trail, yeah, go ahead get a locker - primarily in snow/ice, forget auto lockers & spools, try to find a limited slip diff, or a selectable locker - both of which are going to be pricey.
93 - 1.3 Suzuki Swift GLX
98 - 1.8 Mitsubishi Pajero iO
98 - 2.0 Suzuki Grand Vitara