On Thursday, March 3, 2016 at 12:51:52 PM UTC-5, wrote:
When flying for a badge or record, one will be flying a closed course that involves a 1km long start/finish line. To complete the task, one must cross the finish line no lower than 1,000m below the start altitude.

As the pilot crosses the start line, the computer should calculate a finish altitude based on the actual start altitude.

The computer should also represent the start finish line as *precisely* 1km so the pilot is able to navigate to an end if there is an urgent need to turn immediately after crossing the line.

Since it's advantageous to approach the start line at maximum speed, then pull up immediately after crossing, an audio alert will help keep the pilot's head out of the cockpit. We already have FLARM and airspace voice alerts, so how about "Two seconds...Start"?

ClearNav only provides a start time, not altitude.

How about other computers?

5Z

There are a number of loggers that will cover "certain records" that will be accepted (based on declaration).
It appears that you want a device that, "Is accepted as well as add's other info in realtime (exact start/finish lines & altitudes)".
Is this correct?

I believe all approved loggers will cover the pertinent data (log it for future review, 3D with lat/long/alt & time stamps), but may not show it as you are flying.