I added some minimal polish like an undo command, a minimal GUI accessible via a short-lived link it sends us on request where we can add and edit recurring bills, subscriptions, and upcoming one-time or yearly major expenses. It has support for debts/loans (we can do "cc <debt> <amount>" for increasing debt, e.g. by paying with a credit card, and "pay <debt> <amount>" for payments). It sends us nightly and weekly reports letting us know progress towards savings goals and warning us if we're about to run into a tight spot based on what it knows about our spend rate, and upcoming bills and big expenses. It also bugs us if it notices we haven't transferred anything to savings recently.
The fact that it doesn't sync automatically with our bank accounts is actually a feature, because the ritual of having to text it whenever we spend money forces some mindfulness of our spending habits, and the regular reports (where it chides us if we're not saving much or exceeding our spending goals) add some gamification -- we joke about how we want to make it proud of us. :)
That said, yours looks a lot more full-fledged than mine. Mine can only record transactions and then send a response (which it reads calculated from the spreadsheet based on the last transaction, which I'm very proud of for the level of customization it provides), but I've been noodling over how to add custom commands.
FTR, I shameless stole my idea from an earlier HN comment sometime last year; if you're considering implementing a SMS/spreadsheet system yourself, I'd check it out https://news.ycombinator.com/item?id=17313321
Edit: I really am happy with my solution because it basically lets you take any google sheets based transaction you have and add SMS as an input method.
Edit 2: Sorry if you encounter any rough edges if you go to use BYOB - I haven't marketed it widely, but my wife and I do use it. Any feedback is very much welcome.
Edit 3: If you don't want the manual import of transactions (but do want the freedom of a spreadsheet) then I'd suggest TillerHQ instead https://tillerhq.com I haven't used em, but I came across them when doing research before launching BYOB.
I also like that yours is generic -- I'm curious what other use cases might exist for an SMS based query system for sheets.
Another minor feature I added was lists so that my partner and I could keep our shopping list synchronized -- I could imagine it working well for that too
As for queries, I'd like to add queries to get the categories and query the amount left in a category. But that's more special casing - maybe it's a purist in me. I'm leaning towards letting people define a keywords area with three columns - the first is the word to trigger the command, the second is where anything after the keyword gets put (in some sanitized manner - like stripping whitespace) and the third would be the place to read the response.
I like the shopping list idea.
I haven't really taken the time to polish up some operational bits (we have really good logging/metrics where I work, and I miss it) or to market it though. So it's basically just my wife and I right now. I think the push to get something shipped (and my perfectionism) drained me, but reading this stories comments has been invigorating, and I an probably go about improving things in a more measured manner.
I totally get the benefits of ritually entering though. I’m definitely lazier about non-credit card transactions now... motivation to expand my program to other types of accounts and get fully automated!
We then add categories manually to all transaction on the YNAB app, so... we go through each transaction every couple of days.
Which is probably totally fine for most use cases, but I plan to port it to SQLite and open source it soonish.