Yes, Sony NS-WS623 is meant for the rough usage and it is both - waterproof and dustproof.
Yes, Sony NS-WS623 does have NFC connectivity option.
Sony WS623 has 4GB internal memory and you can further expand it up to 16GB with the help of MicroSD card.
Sony WS623 comes with LED indicator. If it is not fully charged and require charging - it will show orange light and when it is fully charged - it will show green light.
You can check the charging status with the lamp ( 3 ).
While the battery is charging: orange when charging is complete: green