Krias Shema She'Al Hamita

Krias Shema Al Hamita (Hebrew: קריאת שמע על המטה, Bedtime Shema) is a Jewish prayer recited before retiring at night. It is centered around "Krias Shema" with additional verses and requests.

According to Rashi one fulfils his biblical obligation of the saying Shema in this prayer and not when he recites the Shema in the Maariv prayer, being that it was costumary to pray the Maariv prayer while still day (before the time of the obligation).

Source of the prayer
It says in the Talmud:

"Even though one has recited the Shema prayer in the Synagogue, it is obligatory to recite it on his bed"

Additionally it says:

"One that goes to sleep on his bed says 'Shema Yisrael' until 'Vehaya Im Shamoa' and then says the blessing of 'Hamapil'

Additions to the prayer
In the Babylonian Talmud the custom of Rabbi Yehoshua ben Levi is brought that he used to add Psalm 91 and Psalm 3 which are help against the demons.

As the generation unfolded additional Psalms, verses and prayers were added. Customs in this matter vary. Even though it is not obligatory to add Psalms it is generally expected to do so.

The Rishonim argue whether one is to say the portion of "Vehaya Im Shamoa" and those who say one should also recite the third portion of Shema.

According to various customs, which are founded on the Arizal, the prayer also includes the confession prayer in order to confess and clean the sins of the past day. There are some customs which include Psalm 91, 51, and, 121. Additionally there are those that add the prayer of Ana b'Koach and Psalm 67.