Just got my Amazon Nexus 6 delivered and hunted down the cheapest Sprint SIM card for Ringplus service.
This is a good deal on a Sprint SIM card for RingPlus for anyone with a newly acquired phones like the Nexus 6 on BF. My local Bestbuy carried the Sprint SIM cards:
SIMGLW426C $2.99 (nano SIM)
SIMGLW446C $4.99 (nano SIM)
Both SIM will work with the Nexus 6 according to Discourse [ringplus.net]
I purchased the cheaper 426C and it registered fine with Ringplus with my Nexus 6!
Sure beats the $10-$15 SIMs from Ting, R+, etc. with immediate gratification to boot.
There's no online link, it's in store only!