Ask HN: Kicked out by co-founders – what are my options?

Last year I won a hackathon contest with a large group including only one other dev. After the contest we decided to keep working on the project. For a couple of months I played a central role developing the fundamental product concept, business strategy, legal approach, and the coding itself. Periodically I raised concerns that we still hadn't formalised equity share. My concerns were dismissed.

I discovered two of the non-devs had applied to accelerators without asking the team, despite me making it clear that in my opinion we didn't need outside investment. I handed over my work-in-progress and emailed the team saying I was moving to the "advisor tier" which the two had previously described as coming with "a small share of equity", and received positive replies from them. Since then I've been contacted by the other dev for assistance (he'd never heard of node.js - let alone the rest of the tech).

Less than a month later they asked to meet to give me a "token of [their] appreciation". They then ambushed me with an IP transfer agreement and told me that in their opinion I deserved no equity. I didn't sign it.

I contacted them explaining that if they wanted to buy me out, and retrospectively change our relationship, I would expect to be paid for the consultancy I'd provided, and quoted a fair fee. After 7 weeks I've chased them a few times and received a single request to meet in person (I declined as I want written records of all exchanges). The core two and the other dev have since enrolled in an accelerator - and therefore presumably lied about owning the full IP when they gave them equity.

What are my options?