See the recent Canadian case of the thumbs up emoji signature [0]. The bar for a legally binding contract is much lower than what most people believe. The main thing you need is to be able to prove that the other party actually did express their assent to the contract. In the thumbs up case, who sent the text was not disputed, so the issue hinged on whether a reasonable person would interpret thumbs up emoji as expressing assent.

[0] https://news.ycombinator.com/item?id=36618650