Anyone here have any experience with a product called Tracer Arrow (lighted nock)?

http://www.tracerarrow.com/

Have been looking at their website and at first I thought it was pretty gimmicky but upon further thought it actually might be useful especially during early or late day shots when light is very low –

I am guessing that you cannot simply exchange your existing nocks for these as the tracer nocks would be heavier and change your FOC and your would also have to re-sight your bow.

Any insights would be helpful