Low-Latency internal CCTV suggestions?

[Ru_C]

Hi all, am just upgrading my studio security, & I was wondering if anyone had suggestions re:low-latency CCTV?

Reason being, I was hoping to put in a system that would allow me to visually cue musicians in one my live rooms (that doesn't have line-of-sight).

All the systems i've looked at in shops have a notable lag in them which wouldn't be a problem for the intended use, but are hopeless for this.

I realise the older analog 'TV lines' systems don't suffer from this, but I wanted to fit something modern that could be monitored off-site from my phone etc.

Any ideas?