I am finally, finally buying a Korg OT-120, an electric tuner that supports Pythagorean temperament! And, between the Amazon.com discount price and $50 of credit card "rewards" coupons, I'm getting it for under $25!
I think it's taken me so long because I had the Korg OT-120 pegged in my head as "expensive outlay." Over $100! I could buy several books or CDs for that! But it's also really well past time I got it. My ear isn't good enough to do "circle of fifths" unassisted tuning; I can barely hear the resonance on the wire harp and don't hear it at all on my other instruments. Even on wire, I seem to hear it quite a few cents on either side of true tone, so I just don't trust myself to get it right that way.
Gut strings will likely be the next major investment; we'll see how long it takes for me to get around to that.