Well, let's take a look at it, to see what it means:
"Hear, O Israel: The Lord our God is one Lord: and thou shalt love the Lord thy God with all thine heart, and with all thy soul, and with all thy might. And these words, which I command thee this day, shall be in thine heart: and thou shalt teach them diligently unto thy children, and shalt talk of them when thou sittest in thine house, and when thou walkest by the way, and when thou liest down, and when thou risest up. And thou shalt bind them for a sign upon thine hand, and they shall be as frontlets between thine eyes. And thou shalt write them upon the posts of thy house, and on thy gates." --Deuteronomy 6:4-9
First things first: if you don't have kids, you can't teach it to them, nor could you write it on your door posts without a house, etc.
Secondly, to put them in your heart, and on your hand, and between your eyes, is not referring to something that is done physically, but spiritually.
Concerning praying and talking about them, I do it more than what it says to: does that mean I'm breaking the law, by doing it more than it says? of course not: the prescription plainly means, that we are to be filled with His word, in all aspects of our lives, thus it will flow from us, in all that we do.
For example, if you have a house, you should put it on the door posts, and gate posts, and decorate your house with His words, as many people enjoy to do today. But if you prefer to decorate your house with worldly idolatry, and perversion, and vanity, instead of wholesome reminders of His word, then know for yourself, that what is within you, and what you are drawn to, is not His word, but the world.
Take me, for example, I love portraits of Noah's Ark, and the scriptures printed on them, reminding me of God's salvation, and the beauty of His creation: those kinds of things I love now because I love God; but before, I preferred pornography and violence, and many kinds of fantasy, especially in movies, because I loved the excitement and delusion of pleasure, and the detachment from reality it provided; but now I hate those things, because now I can see them for what they are, sorcery and vanity.
Christians fulfill the righteousness of the law, because we do it from the love we have for God, not by some external motivation, such as being stoned to death.
Me, and others like me, are the proof today, against the old covenant, for we do what is right by our new conscience toward God; not by the cost of some animals life, nor by the fear of stoning, but solely by the love of God; thus the law is perfected in us.
When once a Jew would behave for fear of having to pay the price, whether it be in the form of one of his animals, or money, or his own life, now, by the New Covenant, he is motivated solely by what is right, by the life of Christ, Who already paid the price, once, for all our lives--if this doesn't engender love in a man toward God, then nothing will.
Concerning Leviticus, and the feasts (I'm going to get in trouble with some for saying this): I don't think they are required, but I do think they benefit us.
--I must be clear, that I am fundamentally speaking from ignorance concerning this, and coincidentally, that, in it of itself, is another reason why I don't think they are required: not because I've rejected the knowledge concerning the feasts, but because I just don't have it, yet I am Christian indeed; therefore, I have concluded that they are not required for salvation, BUT AND IF, someone would show me that they are, then I would immediately, repent to keeping them, and adopt them into my life, straightaway, period.
Think of it, people love the so called 'holidays' of the world, but what about the holy days of God? --I'm suspicious of that also.
