Before you embark on soldering a Bluetooth chip onto the thing I would recommend something like [https://www.amazon.com/KOKKIA-Transmitter-authentication-capabilities-generation/dp/B004SH40BQ/ref=pd_day0_hl_107_2/140-8859559-5906731?_encoding=UTF8&pd_rd_i=B004SH40BQ&pd_rd_r=fd80258e-3481-11e9-ba4c-998c19a870f7&pd_rd_w=8fGG2&pd_rd_wg=Viz4u&pf_rd_p=ad07871c-e646-4161-82c7-5ed0d4c85b07&pf_rd_r=JMM9GCKEA2M9X01XMER1&psc=1&refRID=JMM9GCKEA2M9X01XMER1|this]:
[https://www.amazon.com/KOKKIA-Transmitter-authentication-capabilities-generation/dp/B004SH40BQ/ref=pd_day0_hl_107_2/140-8859559-5906731?_encoding=UTF8&pd_rd_i=B004SH40BQ&pd_rd_r=fd80258e-3481-11e9-ba4c-998c19a870f7&pd_rd_w=8fGG2&pd_rd_wg=Viz4u&pf_rd_p=ad07871c-e646-4161-82c7-5ed0d4c85b07&pf_rd_r=JMM9GCKEA2M9X01XMER1&psc=1&refRID=JMM9GCKEA2M9X01XMER1|https://www.amazon.com/KOKKIA-Transmitter-authentication-capabilities-generation/dp/B004SH40BQ/ref=pd_day0_hl_107_2/140-8859559-5906731?_encoding=UTF8&pd_rd_i=B004SH40BQ&pd_rd_r=fd80258e-3481-11e9-ba4c-998c19a870f7&pd_rd_w=8fGG2&pd_rd_wg=Viz4u&pf_rd_p=ad07871c-e646-4161-82c7-5ed0d4c85b07&pf_rd_r=JMM9GCKEA2M9X01XMER1&psc=1&refRID=JMM9GCKEA2M9X01XMER1]
If you still want to get crazy you can try [https://www.instructables.com/id/Bluetooth-IPod-Classic/|this]:
[https://www.instructables.com/id/Bluetooth-IPod-Classic/|https://www.instructables.com/id/Bluetooth-IPod-Classic/]
Good luck sir!