How to handle multiple input pins at once? I am relatively new to Arduino platform and not know much. I am working on a Bicycle speedometer with turn and stop indicators.

I am planning on connecting an inductor magnet to calculate the rotation of my front wheel while providing the following services from the same arduino board:


Input horn and turn indicator switches.
Output to turn indicators. 
Stop light when one of the brakes is
applied.


While I am sure of how to connect all the sensors, except the magnet, I am not sure how to handle the various inputs and the outputs at once. 

I must be able to horn and stuff while the indicator blinks at a regular interval all the while the monitor keeps displaying my speed and distance covered.

Any reference or help would be greatly appreciated.
Thanks in advance.

Bharath. S.
How fast do we need to read the magnetic switch to not miss any pulses? I'll make some working assumptions:


Using 700c wheel and 28mm tire [assumed; adjust as necessary]
Rolling radius 2.1m [from here; there are other ways to arrive at this]
Max speed 22 m/sec (50mph), [working assumption; adjust as you see fit]
Magnet and switch interact for at most 3% of a rotation, [WAGuess]


The wheel will have to turn at ~10RPS at max speed giving a pulse period of 100ms. The pulse width will be at most 3% of that, or 3ms.

Your service loop would have to execute in somewhat less than 3ms, every time, in order to not miss any wheel pulses and that's if I haven't been too optimistic about the pulse width. I'd personally assume a 1ms maximum loop time, then test it on the road by sampling &amp; logging wheel-pulse level with an Arduino at at least 10x that rate or 10+KHz.

Or I'd go with an interrupt-driven wheel pulse period timer not width) to ease the constraints on the main loop.

The main loop need only poll your turn, brake, and horn switches and a timer for blinking the turn signals. Even if the timing is a little erratic for some reason, no harm is done, and nothing is likely to be apparent to the rider or other road users.