"Dust sweeper" is a Hive service which upvotes your posts (including comments) with upvotes less than $0.02 so that you still get the author reward. (It is not necessarily a dapp.)
Specifically, it scans your posts, and automatically upvotes any of them that meets the following requirements:
The way it upvotes is that it votes with only enough voting percentage such that your post will have a reward of exactly $0.026 at the time of its upvoting to amount for the possible weakening of Hive token value at the end of the 7 days voting period. It then reduces your balance in their database exactly what you received as an author reward - no loss, no profit.
To use their service, just send any HIVE or HBD to @dustsweeper (note that their service will pause on you if your balance on them is less than 0.03 HIVE, approximately just enough to cover one vote, so nothing unfair here). A memo is not required, unless you want to gift the service to another user, for which you will use the syntax "to:" followed by the username of the recipient (without the @ tag). For example, if you want to gift the service to me, you will add a memo "to:anonymouser". Anyone who is already a
@dustsweeper "client" who gets gifted will simply have their balance increased.
P.S. Thanks to @fw206 for introducing me to the service, and for gifting me 2 HIVE worth of dustsweeper credits.