We did this in 2006 to 2009. My first entrepreneurial venture. We even had proximity marketing as part of the offering.
Later, in 2012, we pivoted to cab headrest screens, specifically RedCab and Metro Taxi, branded private cabs in Lagos.
It did not scale for two reasons:
1. The logistics of scale are clumsy. Usually, you have to deploy your own screen in those locations. That implies a sunk cost of hardware, which eventually will make your balance sheet suck.
2. It is impossible to measure impact, which means the big brands won't go for it. Small brands already use the Internet and social media, which have built-in measurement tools.
What we found at that time was quite interesting. Small brands were not going to pay enough to sustain a rollout at scale, while the medium was just too small for big brands. We eventually scrapped it.
May these guys find better success.