The journal has a RedeemVoucher event, but at the moment it doesn't provide any information about the faction for which the redemption occurs so it's no use as a bounty tracker. FD have this on their list to look at, so perhaps come 2.3 it will be useful.
But would this event be able to track just a generic bounty turn in? I'm not tracking factions, just the fact that I have a bounty/bond to redeem. It seems that the redeem voucher event would trigger when the bounty/bond is redeemed. That way I could use this to clear the tracking variable I use.