Knox is nostr:nprofile1qydhwumn8ghj7emvv4shxmmwv96x7u3wv3jhvtmjv4kxz7gprpmhxue69uhkummnv3exjan99eshqup0wfjkccteqy2hwumn8ghj7un9d3shjtnyv9kh2uewd9hj7qgkwaehxw309aex2mrp0yhx6mmnw3ezuur4vghsz9mhwden5te0wfjkccte9ec8y6tdv9kzumn9wshszxthwden5te0wfjkccte9eekummjwsh8xmmrd9skctcqyqzxrl97e3xrxazrnyeddw83zf5uekmue9e667js4cmzmvf4536d6swz3vl tool. But it's not desktop (and I guess neither is Keycast). They're both server tools.
nak by nostr:nprofile1qqsrhuxx8l9ex335q7he0f09aej04zpazpl0ne2cgukyawd24mayt8gprfmhxue69uhhq7tjv9kkjepwve5kzar2v9nzucm0d5hszxmhwden5te0wfjkccte9emk2um5v4exucn5vvhxxmmd9uq3xamnwvaz7tmhda6zuat50phjummwv5hsx7c9z9, keycast by nostr:nprofile1qqspwwwexlwgcrrnwz4zwkze8rq3ncjug8mvgsd96dxx6wzs8ccndmcpzamhxue69uhkv6tvw3jhytnwdaehgu3wwa5kuegpp4mhxue69uhkummn9ekx7mqpzpmhxue69uhkummnw3ezuamfdejsul2dhz, and I can never remember the name of nostr:nprofile1qqsqgc0uhmxycvm5gwvn944c7yfxnnxm0nyh8tt62zhrvtd3xkj8fhgprdmhxue69uhkwmr9v9ek7mnpw3hhytnyv4mz7un9d3shjqgcwaehxw309ahx7umywf5hvefwv9c8qtmjv4kxz7gpzemhxue69uhhyetvv9ujumt0wd68ytnsw43z7s3al0v's tool
Discussion
The only requirement would be on and connected to the Internet 24/7 with docker installed. A desktop or laptop running running docker could do this.