The Shulhan Aruch (Orah Haim 219:4) rules that if a person is obligated to recite Birkat Ha’gomel, but instead of reciting it himself, he hears somebody else recite the Beracha for him, and he then answers "Amen," he fulfills his obligation. In such a case, the Shulhan Aruch writes, the one reciting the Beracha should modify the text of the Beracha, and recite "She’gemalcha" instead of "She’gemalani," since he recites the Beracha for somebody else, and not for himself. The Rama (Rabbi Moshe Isserles of Cracow, 1525-1572), in his glosses to the Shulhan Aruch, explains (listen to audio recording for precise citation) that this recitation is not considered a "Beracha Le’batala" (Beracha recited in vain), because the one reciting the Beracha rejoices over the fact that his fellow was saved. He expresses joy and praise to God for rescuing his fellow from a dangerous situation, and thus this Beracha is perfectly valid.
The Mishna Berura (commentary by Rav Yisrael Meir Kagan of Radin, 1839-1933) notes that a common application of this rule is a husband’s recitation of the Beracha on his wife’s behalf. If a woman must recite Birkat Ha’gomel, but she cannot attend the synagogue or she does not know how to recite the Beracha, then her husband can recite the Beracha on her behalf. If she is present when he recites the Beracha, then he recites the text of "She’gamalech"; if she is not present, such as if the husband recites the Beracha in the synagogue and she is home, then he recites "She’gamal Le’ishti."
The Mishna Berura then proceeds to qualify this ruling of the Shulhan Aruch, asserting that it allows reciting the Beracha only on behalf of one’s family member or close friend. In such cases, one indeed feels genuine joy over the person’s safe emergence from danger, and he may therefore recite the Beracha on that person’s behalf. When other people are rescued from danger, one does not necessarily experience feelings of joy and gratitude, and he therefore cannot recite the Beracha on their behalf. The Mishna Berura concludes that because of this significant restriction, one should not recite Birkat Ha’gomel for another person, except for one’s father or Rabbi, as in such cases he indeed experiences immense joy. For others, however, one should not recite Birkat Ha’gomel.
Notwithstanding this discussion, Rav Shemuel Pinhasi, in his work Ve’chol Ha’haim (p. 23; listen to audio recording for precise citation), observes the common practice not to allow reciting Birkat Ha’gomel on someone else’s behalf under any circumstances. Even if the person who must recite the Beracha is one’s family member, and even if that person is unable to personally recite the Beracha, he should not recite the Beracha on that person’s behalf. Of course, if one is himself obligated to recite the Beracha, then he may have the other individual in mind so he can fulfill the obligation through his recitation. For example, if two people traveled together, after the trip one can recite the Beracha on behalf of both of them. However, if a person had already recited the Beracha, or is not obligated at all in Birkat Ha’gomel, he may not recite it on someone else’s behalf. Birkat Ha’gomel differs in this respect from other Misvot, where Halacha allows one to recite the required text on behalf of another even if he had already fulfilled his obligation. Since Birkat Ha’gomel is a personal expression of gratitude to the Almighty, only the person who was rescued from danger may recite the Beracha. This is also the ruling of Hacham Ovadia Yosef, in his work Hazon Ovadia – Berachot (p. 355).
Summary: If a person emerged from a dangerous situation and is therefore obligated to recite Birkat Ha’gomel, he must recite the Beracha personally; he may not ask somebody else to recite the Beracha on his behalf. However, if two people are obligated to recite Birkat Ha’gomel, one may recite the Beracha on behalf of both of them.
