Siemens and Flarion are developing a high-speed wireless internet technology suited to, well, the high-speed customer:
FLASH-OFDM® systems enable users traveling at speeds of up to 250 kilometers per hour to utilize data services at average downlink speeds of 1 to 1.5 megabits per second, capable of bursting to 3.2 megabits per second in individual cases. The uplink typically offers users an average experience of 300 - 500 kilobits per second, bursting to 900 kilobits per second. With latency of only 50 milliseconds, the system is extremely well suited for enterprise or interactive applications.
So at last we have something for the black-windshield Mercedes and BMW crowd who strive to approach these speeds on Latvia's less than high standard highways and basically gonzo drivers (381 dead so far this year and counting...). As for trains, one of the best known trains (for tourists) is the Little Train (Mazais bānītis) where you can hop off and pick flowers or mushrooms and then catch the train again at a slow jog (so one says, I haven't tried it).
On a more serious note, it will be interesting to check whether Triatel, the CDMA-450 operator starting commercially in November, will be looking into this. Or Lattelekom, for that matter (although they are aiming at rural shacks, which don't move very fast).