Coin flipping with limited communication between participants
As fgrieu pointed out, Alice and Bob must have somehow come to some kind of agreement before the random beacon is generated.
Would either of these techniques work for you?

use the random beacon directly

They could agree ahead of time that "Alice wins if the first random bit sent by the NIST Randomness Beacon on 2015-11-02 at 11:59 is a 0, and Bob wins if that bit is a 1."

Randomness beacons allow a person to prove that the random number (or any hash value calculated from it) was generated after some particular time.

use Alice's message with trusted timestamping

There are ways of doing trusted timestamping to prove that Alice knew a message before some particular time.

They could agree ahead of time that "After Alice commits to a single message by including that message in the Bitcoin blockchain as part of a transaction sending a tiny amount of bitcoin from Alice to Bob sometime during the day of 2015-11-01, and then later the NIST Randomness Beacon on 2015-11-02 at 11:59 generates some random data, Alice wins if the first bit of hash(message, beacon) is a 0, and otherwise Bob wins."

(If the message is long, it would be better to store only the hash of that message in the blockchain as a commitment to that message).

There is no direct communication from Alice to Bob or from Bob to Alice before the beacon transmission,
although this particular system requires some two-way communication between Alice and the Bitcoin system before the beacon transmission.


  Alice may generate several messages and timestamp them before the
  random beacon is generated. Then, after the random beacon is
  generated, she can choose the message that yield the result that
  favors her.


With this system, after the beacon transmission, Bob can fairly easily inspect the Bitcoin blockchain for that day and see if Alice tried to cheat by sending small amounts of bitcoins to him over several transactions that day, each transaction with the hash of a different message.
(Bob could inspect that blockchain even before the beacon transmission, although you could argue that would count as a message from Alice to Bob before the beacon transmission).


  How can we prove that the timestamp was generated before the random
  beacon?


That is a hard problem, but that is the problem that Bitcoin was designed to solve.