Add this to the "it seemed like a good idea at the time" list.
Now perhaps it's down to the way I use Truphone, but for me it's pretty much useless. The idea of the button is that it shows whether my phone can take Truphone calls right now, or whether they'll be forwarded elsewhere (at a possible cost to both parties). There's one fatal flaw in this apparently useful button, I haven't and won't give my Truphone number out, as I don't believe in the concept of me paying to receive calls. So, I only connect the Truphone app to my WiFi when I need to make free international calls, at which I must admit it is very good, with a sound quality that makes Skype look like the toy it is.
If this all makes me sound like some curmugeonly old luddite, then so be it. I'm a big fan of VOIP, but with the cost of voice calls approaching zero there is very little benefit for me (YMMV) in fiddling around and gaining yet another phone number.
Case in point, I have more inclusive minutes every month on my mobile contract than I use, so almost all UK calls to landlines or mobiles are effectively free from my mobile. My landline provider offers free calls to everyone using the same provider, which is 2/3 of my regular calls, and cheap rates otherwise. So going through some hassle to save a very small sum really isn't worth it.