There are plenty of Oppo compatible smartwatches out there. But do note that most of them are of low priced make.
OPPO F1 Compatible and Certified Bluetooth Smart Watch
This model is compatible with most of the Oppo phones. It has SIM card slot and NFC support. It also comes with remote camera feature. Though there is no auto focus for the camera. Also one more thing to note here is that there is no programmable option there. And there seems to be no batteries included with the device. It costs 1,690 Rs on Amazon.
You can get it on : http://www.amazon.in/OPPO-F1-Compatible-Certified-Replacement/dp/B01I5KYG1K?&linkCode=xm2&camp=2025&creative=165953&creativeASIN=B01I5KYG1K&tag=578279-21
OPPO F1 Compatible and Certified Smart Watch by Captcha
This is another smartphone watch, with some decent reviews. It comes up with charging cable and also 180 days warranty. There is a SIM slot but lack of NFC support. It has 16GB of memory card support. It costs 1,384 Rs on Amazon.
You can get it on : http://www.amazon.in/OPPO-F1-Compatible-Connectivity-Replacement/dp/B01HXWFQWE
Oppo Neo 7 4G Compatible Smart Watch by Captcha
This is another smart watch from Captcha. The model seems to be supporting SIM card slot with NFC support. It has support to bluetooth. It also support various audio formats such as MP3, MP4 and others. For camera, it doesn't have autofocus support but it gets the job done. It is priced at 999 Rs on Amazon India.
You can get it here: http://www.amazon.in/Oppo-Neo-4G-Compatible-Ceritfied/dp/B01M70QFNM/ref=pd_sbs_147_4?_encoding=UTF8&psc=1&refRID=0MP73QSYEN0FK9F02CWT
There are few others which are generic in nature but support most of the Android based devices that you may want to look at.
1. ELV Generic Smartwatch
2. Bingo T50
3. eCosmos Smartwatch.