So today on the 13th of march the 1.5 Update or 'The Redstone Update' came out, this is an updatefeaturing many new redstone and transportaion items.

Added Redstone Comparator (used in Redstone logic) + Added Hopper (collects items and moves them to containers) + Added Dropper (similar to Dispensers, but always drops the item) + Added Activator Rail (activates TNT Minecarts) + Added Daylight Sensor + Added Trapped Chest + Added Weighed Pressure Plate + Added Block of Redstone + Added Nether Brick (item) + Added Nether Quartz and ore + Added Block of Quartz, with half blocks and chiseled variants + New command: /scoreboard + New command: /effect + Containers and mobs can have custom names * Inventory management has been changed, for example you can drag-place items over slots * Texture packs now have separate images for each block and item, and can have animations * Nether Quartz Ore now spawns in the Nether * Smooth lighting now has three settings (none, minimal, maximum) * More detailed death messages * Some hostile mobs now are harder in Hard difficulty * Many, many, bug fixes - Removed Herobrine

Redstone comparator: The redstone comparator, similar to the repeater will re-transmit a signal, just like a repeater would, but there are 2 signal imputs one coming into it straight and one from the side. Lets assume that straight= Signal A, the side= Signal B and >/< = less than or futher than in legnth (blocks). If signal A is on it will pass through the signal, but if signal A>signal B, signal A will not pass through. However if Signal A<(or equal to)Signal B, signal A will pass through. these can be used to block or stop a signal passing.

Daylight sensor: The daylight sensor is imilar to a solar panel in real life, the more collective sunlight the higher amount of energy it will produce. Dependent on the time/height of the sun, the stregnth of the signal will be different, after sun-down no signal will be transmitted. these can be used to make street lights, night lights ect.

Weighted pressure plate: in gold(light) or iron(heavy). gold will take a little ammount of thrown items to emmit a 15 block strong signal whereas the iron will take up to 9 stacks to do the same.

Hopper: useful to transfer items via chests/droppers ect.

trapped chest: just like a normal chest but when opened, it emmits a signal.

there are many more items, update your minecraft to find out, also I wish that you would watch my video which explains everything.