Two of the four parshios contained in the tefillin are found at the conclusion of parshas Bo. Many of the laws of tefillin are halacha l'Moshe miSinai, (i.e. taught to Moshe by Hashem during his tenure atop Mount Sinai.) Among these laws is the requirement for tefillin to be black square boxes containing four paragraphs from the Torah that reference the mitzvah of tefillin. Another law requires that the tefillin worn on one's arm has one compartment that contains the four paragraphs on one long piece of parchment, while the tefillin worn on one's head has four compartments, each housing a separate paragraph.
The Torah does not give a reason for the aforementioned difference between the two tefillin. The Meshech Chachma (13:9) suggests an interesting approach. Regarding the Bais Hamikdash, Shlomo Hamelech speaks for Hashem (Melachim 1, 9:3) and declares, "My eyes and My heart shall be there all the days". The Meshech Chachma takes the liberty of extending this relationship of Hashem directed to the Bais Hamikdash, to the connection of man to Hashem when he dons his tefillin (see Rambam Hilchos Tefillin 4:24.) The Tefillin of the hand placed across from the heart corresponds to the love that Hashem has for all Israel. As a parent loves all their children equally, so does Hashem love all Israel, and hence the four parshios are included on one klaf (parchment) in tefillin worn on one's arm. The tefillin on one's head is placed between one's eyes and hints at Hashem's hashgaca pratis (divine providence), his watching over us. In this realm there are four compartments, corresponding to the four types of Jews. The Medrash (Vayikra Rabbah 30:12) teaches that the four species of esrog, lulav, hadassim and aravos correspond to those individuals with both Torah and good deeds, those with only one or the other, and those with neither. Commensurate with one's accomplishments is His divine providence.
With the above teaching we can now understand and appreciate the teaching of the gemarah (Menachos 37b) which identifies that the tefillin on one's head is to be worn on the high part of the head. The Talmud asks what is the source that the tefillin are to be donned above one's hairline and opposite the space between one's eyes? The answer given is a gezara shava, one of the thirteen rules by which the Torah is expounded. When similar words are used in two independent laws, there is a Sinaitic tradition that they are meant to shed light one upon the other. The Torah in parshas Bo (13:16) mandates that tefillin be "between your eyes", and the Torah teaches (Devarim 14:1) regarding a mourner "you shall not make a bold spot between your eyes for the dead". In both places the Torah mentions the space between your eyes; the gezara shava teaches that just as regarding a mourner it must refer to the high part of the head, a scalp, as that is the place to potentially make a bold spot, so too regarding the tefillin the Torah mandates the it be placed on the high part of the head.
I believe the above cited gemarah is teaching a great deal more than where to place the tefillin; the Talmud is teaching an important philosophical lesson of the tefillin. In the very place that others would rip out their hair in an expression of despair and helplessness over the death of a loved one, our Holy Torah directs us to place the tefillin, a symbol of our faith in God, who in His Divine Providence controls and directs everything. Thus, the tefillin which contain the oneness of G-d as found in the Shema and the exodus from Egypt bolster the belief and faith of the Jew, enabling him to accept and appreciate all that Hashem does. The gezara shava not only explains the where of the Tefillin, but the why as well.