The main point with LN is the need to monitor the blockchain. The reason for this is to detect if the counterparty misbehaves by publishing an old channel state to the blockchain. For a node running on a server, that is not a big problem since it is always online, but mobile nodes might go offline for days, so how do we deal with this issue?
The need to monitor the blockchain actually only exists if the channel is used in both directions: if you are only paying, any outdated commitment transaction will be more in your favor than the current one, so there is really nothing to do!
But in case of two-way payment channels, this seems to be resolved by "trustless third-party watchers". Since I can't find much literature on the internet about them, I was wondering, how do they work and how exactly are they trustless? For that matter, how do you actually trust that anybody is going to publish on your behalf, and why? Are there incentive mechanisms in place for this to be completely trustless?