[MT-AU Public] Out of Band access options

Hi All, I am interested to know what people are using for OOB management access to remote sites. We have a mix of routers from TPLink to Mikrotik with 3G/4G or DSL lines into them which we then jump through to get to gear on a site, we are currently reviewing our options with a view to standardising on one brand/model if possible. Mikrotik Routerboard is a good option, but for DSL connections it needs a modem, and if using 3G/4G the modems for PCIe are a bit pricey still, just wondering what others are doing and what the most cost effective approach would be for such a little utilised component but one that is really important for remote sites. Regards Paul