I don't know about the android app. I have tested 4-5 of them & only one
worked for me. But still, it wasn't displaying my stream properly so eventually
I had to built my own one. For now, until you are sure that your stream works,
you better test it with computer's browser to be sure.
Another thought is to allow access to "javaw.exe" too, as this is the process.
Also recheck your port forwarding table, sometimes it's just a small mistake
that goes unnoticed & causes all the trouble. What rules have you set? For
example, is it like: TCP traffic from Public Port 8081 to -> 192.168.1.2 Port 8081?
(Btw, what is yawcam's console saying when you activate the stream?)
Finally, keep in mind that some routers (like mine

) reassign the LAN IPs to
different machines after reboot. So, if I forward "8081" to my computer which
has the IP "192.168.1.2", after router's reboot that IP might have been assigned
to my mobile!

(Although I doubt that this is the case for you, just saying.)