GPS would be tricky to receive in a typical hotel or office lobby (i.e. far away from any windows at the ground floor, possibly in an urban canyon).
In Germany (and in neighboring countries), radio-controlled clocks are quite common for this purpose, listening to DCF77 near Frankfurt [1].
Long wave seems to work a bit better than the L-band for indoor propagation, and it probably also helps that the transmit power is three orders of magnitude higher.
I'm not sure if the US has an analogous service – there's WWV and WWVH, but they are shortwave transmitters, and I don't know if wall clock or even wristwatch size receivers are possible for that.
In Germany (and in neighboring countries), radio-controlled clocks are quite common for this purpose, listening to DCF77 near Frankfurt [1].
Long wave seems to work a bit better than the L-band for indoor propagation, and it probably also helps that the transmit power is three orders of magnitude higher.
I'm not sure if the US has an analogous service – there's WWV and WWVH, but they are shortwave transmitters, and I don't know if wall clock or even wristwatch size receivers are possible for that.
[1] https://en.wikipedia.org/wiki/DCF77