The watchman falls under the auspices of the prophetic and intercessory callings -- but not quite. The watchman sees and discerns and then gives warning. The gravity of the watchman's warning calls for clarity, conciseness and plain speech. In other words, there is no ambiguity or 'parable' type voicing from the watchman as there is among other prophetic types. The watchman is a "discerner of the brethren", which means ministry is primarily to the Body of Christ and not the non-Christian world.
The biblical personification of the watchman can be found in Ezekiel. There is a mystical quality to Ezekiel that is undeniable and while many may consider him a prophet Ezekiel was actually a watchman (Ezek. 3:17). Ezekiel was entrusted with many secrets of the Lord, and as such so are the watchmen of today bearers of God's secrets.
With the glorious blessing of holding the Lords secrets comes tremendous responsibility. Failure to walk in the integrity of God's discernment brings a most solemn and grave consequence, a consequence that is accounted in blood!!! (Ezek. 3:18).
The watchman has a view of God's Church that is special and unique. The Old Testament is replete with references of the watchmen inhabiting the high places; towers, walls, mountains, etc. These are all symbolic of today's watchmen where the Spirit of the Lord takes him (or her) to the higher spiritual ground allowing the greater view of Christ's Church, and how the rest of the world revolves around her -- this is the watchman's view!
The teacher has knowledge, the pastor has compassion, the prophet has revelation, the evangelist has zeal and the apostle has authority, but the key characteristic of the watchman is wisdom. The apocryphal book of the Wisdom of Solomon 8:8b says, "she (wisdom) has foreknowledge of signs and wonders and of the outcome of seasons and times."
Ultimately the true watching and discerning is the Lord's: "Except the Lord keep the city, the watchmen waketh but in vain." Psalm 127:1b