I'm wondering whether these is any option to include math mode in tooltip title using bsTooltip() from shinyBS package.
Small example:
rm(list = ls())
library(shiny)
library(shinyBS)
ui <- basicPage(
  headerPanel("Tooltip test"),
  bsTooltip(id = "Equation", title = "\\(\\bar{X} = \\frac{1}{n}\\sum_{p = 1}^{n}X_p\\)", placement = "bottom", trigger = "hover", options = NULL),
  mainPanel(
    p("some text", htmlOutput("Equation", inline = TRUE))
  )
)
server <- shinyServer(function(input, output,session) {
  output$Equation <- renderUI({HTML("<font color='blue'><u>something which needs equation</u></font>")})
})
shinyApp(ui = ui, server = server)
The result (math mode) is not satisfactory:

