How can one claim 50 move rule draw under time pressure? Suppose one player has only 3 minutes of time left in his clock. The position is a draw with opposite colored bishops and neither player can break forward practically. The other player, who has got lots of time left, intentionally plays on to win on time. Since the player under time pressure will not be keeping score, how can he claim if he has completed 50 moves as per the 50 move rule? What is the best solution to this situation in a tournament organized according to FIDE rules?
According to clause 8.5a of the FIDE Laws of Chess (the URL keeps changing so I won't link to it, but you can search), if a player has under five minutes left and the increment is less than 30 seconds per move (or nonexistent), an arbiter or assistant should keep score if possible. This is one reason that a 30-second increment is used these days; both players are required to keep score for the whole game so this situation never comes up.

If the game is played by USCF rules, then according to rule 14F4, if a player has under than five minutes left, he can ask the tournament director to keep track of the number of moves in order to verify a claim that the player makes. (The player is still responsible for making the claim.)