Some time ago Christianity Today had an excellent article on Evangelicals and Mary. I can see where the saying of the Hail Mary would be a problem for Protestants. But the concept of the Rosary to meditate on the Life of Christ while saying set prayers could find valid application in Protestantism.
Why not instead of reciting a Hail Mary recite one of the Psalms while meditating on Jesus. An example would be to recite psalm 22 while meditating on Christ’s death on the cross. Prayer is part of Christian discipline. With all the distractions we have isn’t it good to have a means of turning all our attention to the Lord? This is what the Rosary does for some.
Originally the Rosary was a replacement for reciting the 150 Psalms of David, for those who didn't have a Psalter or couldn't read. So by reciting Psalms as you count off the beads, you're simply returning to the original idea!
Of course, an essential part of the Rosary is meditating on one of the Mysteries, which changes with every ten beads.
Plus there are a gazillion “Scripture Rosary” pamphlets that have a different Scripture verse after each Hail Mary! Or, for those not interested in the Hail Mary, why not say only ONE and then pray completely to God using the Divine Mercy Chaplet shown here:
http://www.ewtn.com/Devotionals/mercy/dmmap.htm
The ideal is not the constant repetition of a mantra. For those who say the Rosary prayerfully (or the Divine Mercy), it is to enter into a Meditation on scenes from the Life of Christ or to lift our minds to God. It is actually a very Christological devotion and the addition of the Luminous Mysteries by John Paul II made it even more so!