Where the walkie-talkies may have an edge over other wireless tech, is that they typically use a longer radio wavelength than more modern stuff (eg. WiFi). Longer wavelengths penetrate objects better, but more importantly they also tend to reflect better from other nearby structures. This enables non line-of-sight communications, eg out the window, off a neighbouring structure, and back in through a different window.

But I still favour the doorbell style solutions -- wired beats wireless for reliability every time.

Cheers