Try this one.
The Ready functions work a little differently in this and a Sourcemod 1.4 dev snapshot is required for IsPlayerReady (though the toggle will work fine on 1.3.x). Also, it's possible that IsPlayerReady will crash the server if I fubar'd the gamedata. Don't test on a live one.
Code:
/**
* Returns whether or not a player is marked as ready.
*
* @param client Client index
* @return True if player is ready, else false
* @error Invalid client or unsupported
*/
native bool:Swarm_IsPlayerReady(client);
/**
* Toggles a player's ready status
*
* @param client Client index
* @noreturn
* @error Invalid client
*/
native Swarm_TogglePlayerReady(client);