the activity tracker 's first start was with fitbit as simple health monitor and it has been developed into the band with other functions such as GPS, counting steps and distance while walking and swimming and a lot of similar players joined into this market. the specialty of these devices which help  people and make them supporters are to quantify their activity how to be close to their goals and share its result with other friends by the ap of connected smartphone.

There are several mistakes in the sentence. Here's the corrected version: "The activity tracker's first start was with Fitbit as a simple health monitor. It has since been developed into a band with other functions such as GPS, step counting, distance tracking for walking and swimming, and many similar players have joined this market. The specialty of these devices, which help people and gain supporters, is to quantify their activity to help them reach their goals and share results with friends via connected smartphone apps."

Corrections made: 1. "Fitbit" should be capitalized as it is a brand name.

2. "As" should be followed by "a simple health monitor" to form a complete phrase.

3. Added a period after "monitor" to create a new sentence.

4. Added "into a band" to clarify the development of the device.

5. Added commas to separate items in a list ("GPS," "step counting," "distance tracking").

6. Added "for" before "walking and swimming" to clarify the purpose of distance tracking.

7. Changed "and a lot of similar players joined into this market" to "and many similar players have joined this market" for clarity and grammatical correctness.

8. Changed "which help people and make them supporters" to "which help people and gain supporters" for clarity and grammatical correctness.

9. Changed "to be close to their goals" to "to help them reach their goals" for clarity and conciseness. 10. Changed "share its result with other friends by the ap of connected smartphone" to "share results with friends via connected smartphone apps" for clarity and conciseness.