Is it just another wallet or do they have something unique, too?
GM nostr โ PV ๐
I just got access to try out nostr:nprofile1qqsrs20qpc4hlq0ef7s3q0k7swlp79q8ys5eex3hxtmg40fccvr4yhspz4mhxue69uhhyetvv9ujumt0wd68ytnsw43qzxthwden5te0wfjkccte9eeks6t5vehhycm99ehkuegprpmhxue69uhkummnw3ezucm0d9hxvatwvshxzurskuxa67 Wallet ๐งก
As a regular user of Bitcoin though, I am just not sure how an on-chain, mobile, hot wallet fits into my financial life.

If I'm going to use a mobile on-chain wallet I'd go with muun (because lightning interoperability) or nunchuk (with a tapsigner or passphrase). I guess Bitcoin via email is cool, but it's still too early for me to even find an opportunity to use that feature.
P.S., I've got 5 invites if anyone wants to try it out, although I assume you need already have a protonmail account.
Discussion
The only unique thing that I know of is that you can send and receive Bitcoin via email if both people have proton.