Question for musicians / bandfolk?

So, our band is having a leeetle problem. Our drummer is not the most metronomic person on the planet. He has talent for the runs and sounds okay, but if there's a simple rhythm, he cannot keep his timing dead on. With wavering rhythm, me, the bass player, starts to wander also, and the rest of the band starts losing it.

I've heard of folks using in-ear monitors with a click track to help things stay on the beat, and I'd be keen on hearing from folks who have ever used these, and how well they work.

I would -love- to go "Okay folks, Stormy Sunday, it's slow, 50bpm, here's the click track *tic... tic... tic...* go!"

We're an older set of players (40's, 1 fellow over 50), we kick along nicely, but I think we need a little assistance. Lots of old-fashionism (though our drummer is currently using an all-electric kit, which is great, because we can go "TURN IT DOWN!" and he can). The other players are rhythm guitar and lead guitar and bass (me). We all have our own amps right now, but we do own and use on gigs a nice 24channel mackie mixer and PA. If it comes down to "we mix everything, we monitor through the mixer, we add the click track to the wireless", then we'll go with that, but I've never done that. :)

Thanks...