Would you use a product that only lives in your text messages?

Tab came out of stealth this week, and TechCrunch reported a $300M valuation. It's a personal assistant you text on iMessage or WhatsApp. The founder said it has its own phone number, computer and wallet, so it does the task instead of telling you how.

I like that there's no app to install. What I'd worry about as a user is checking what it actually did. A chat log isn't a great receipt when money is involved. For anyone building on WhatsApp or SMS, how do you show people what happened after the fact?